Contents
Learning Objectives
By the end of this section, you should be able to:
- Fully describe the Nervous System.
- Explain the types of Nervous System.
- Describe the structure of neuron.
- Describe the structure of the brain.
Some Facts about the Nervous system
- The most complex body system is the Nervous system.
- The nervous system is constantly alive with electricity.
- The nervous system is the body’s prime communication and coordination network.
- It is so vast and complex that, an estimate is that all the nerves in one adult large animal body joined end to end, could reach around the world two and a half times.
What is Nervous system
Every living thing has to maintain homeostasis, amongst other things (in characteristics of living things in ANP 101). The body systems of living things cannot achieve this without a control network or mechanism. The Nervous system is responsible for the control and coordination of all essential functions of the body, and all other body systems, allowing the body to maintain homeostasis or its delicate balance.
Functions of the Nervous System
- The Nervous system gathers information from both inside and outside the body – Sensory Function.
- The Nervous system transmits these collected information to the processing areas of the brain and spine.
- The information is processed in the brain and spine – Integration Function.
- The Nervous system then sends this processed information to the muscles, glands, and organs so they can respond appropriately – Motor Function.
The nervous system is very complex but we are going to stay within our scope.
Nervous System in the different Phyla of the Animal Kingdom
A Unicellular organism lacks a nervous system as all cellular functions are controlled by a nucleus. Nervous systems can only be found in multicellular organisms, but not all. Organisms like sponges which have simple body structures, possess no nervous system. On moving down the different Phyla in the animal kingdom, the nervous system become more complex. For example, the nervous system in cnidarians appears like a diffuse nerve net, Down to the worms which have structures that control body metabolism but no brain, down to other organisms that have nerve structures around several parts of their bodies coupled with a Central brain (with the exception of echinoderms) and a Central cord (found only in vertebrates). The size of the nervous system ranges from a few number of cells in worms to billions of cells in larger animals.
Neuron
Neuron is the basic structural and functional unit of the nervous system.
All nervous tissues from the brain, to the spinal cord, to the ends of every nerve branch, are composed of cells called neurons.
Neuron is responsible for transmission of signals around the nervous system.
Structure of a Neuron
Dendrites
Dendrite is derived from the Greek word 'dendron' which means tree. Dendrites are extensions from the cytoplasm of the neuron cell, and their function is to receive signals, and carry it toward the cell body of the neuron.
Cell Body
The cell body of a neuron is also called Soma. It is the largest part of the neuron, and contains a nucleus and cytoplasm that control the neuron activities.
Axon
Axon are nerve fibers which carry signals away from cell body. Axon end at terminal buttons where they transfer signal to the next neuron.
Schwann Cells
Schwann cells is a type of glial cell that produce myelin or white fatty layer which cover the axon of neurons.
PRO TIP: Along with neurons, found in the nervous system are other specialized cells called glial cells (or simply glia), which provide structural and metabolic support to nerve structures. They are not basically part of the nervous system but they play important support roles.
Myelin sheath
Myelin is a white, fatty, waxy layer which covers the axon, to insulate it from the surrounding fluids and other neurons, and protecting it from interference. This increases the efficiency of transmission of nerve impulses.
Only Axon are covered with myelin, not the cell body. Myelin is produced in the brain and spinal cord by glial cells in a process called myelination . Myelinated neurons are faster in conducting messages as they move through the nervous system. Survival of an organism is dependent on how quickly messages can move through the nervous system: for example, processing spoken language quickly or pouncing on prey.
Node of Ranvier
Node of Ranvier are small gaps between myelin sheaths which cover the axon of a neuron.
Types of Neuron
There are basically 3 types of Neurons according to function:
Sensory neurons: sensory neurons bring signals to the Central Nervous System (discussed below) for processing.
Interneurons: or relay neurons, these are neurons between sensory and motor neurons, found in the Central Nervous System.
Motor neurons: motor neurons carry messages from Central Nervous System to the effectors for action.
PRO TIP: a neuron may be unipolar, bipolar or multipolar.
Impulses
A stimulus is a change in the environment (either internal or external) with sufficient strength to initiate a response.
Excitability is the ability of a neuron to respond to the stimulus, and convert it into a nerve impulse.
All or Nothing Rule: A stimulus is either strong enough to start an impulse or nothing happens.
Impulses retain the same strength along a given neuron, and they are self-propagating – once it starts, it continues to the end of the neuron in only one direction - from dendrite to cell body to axon.
Nerve impulses lead to movement of ions across the cell membrane of the nerve cell (to be discussed in higher class).
Synapse
Synapse is a small gap junction or space in which nerve signals are transmitted from one neuron to another. It is the space between the axon of one neuron, which send out signals that will be collected in the dendrite of another neuron.
The process of transfer of signals from one neuron to another is called synapsis (plural: synapses).
Two neurons that are involved in synapsis do not touch each other.
Signal is transmitted between two neurons in synapsis with the aid of a chemical messenger called neurotransmitters.
Neurotransmitters
Nervous system messages travel through neurons as electrical signals. When these signals reach the end of a neuron, they stimulate the release of chemicals known as neurotransmitters.
Neurotransmitters travel across synapses (spaces between neurons) or between neurons and other body tissues and cells.
They are classified as two types:
- Excitatory neurotransmitters.
- Inhibitory neurotransmitters.
Excitatory neurotransmitters stimulate electrical signals in other neurons and encourage responses from body cells.
Inhibitory transmitters discourage signals and cellular responses.
Through these chemicals, the nervous system regulates the activity of muscles, glands, and its own nerve pathways.
Reflexes
Reflexes are rapid, involuntary reactions in response to a stimulus that's applied to a sensory organ.
Reflexes occur when a sensory neuron passes information to the closest Central Nervous System (not necessarily the brain), and with the help of interneurons, the message is quickly relayed to a motor neuron. An example of a reflex is when you unknowingly put your hand on a hot cooking pot: the sensory neuron in your hand pass the information to your spinal cord, which processes the information that 'this thing is too hot', the information will then be relayed to the muscles in your hand (via motor neurons) to withdraw from the pot. Reflexes occur very fast. The simplest pathway (around the nervous system) by which a reflex occur is called a Reflex Arc.
Reflex Arc
This is the simplest neural pathway by which a reflex occurs. Reflex Arc is the basic functional unit, or smallest and simplest pathway capable of receiving a stimulus and yielding a quick response.
Reflex arc consists of 5 components:
Receptor: reacts to a stimulus and an impulse is generated.
Afferent pathway (sensory neuron): conducts impulses to the Central Nervous System.
Interneuron: consists of one or more synapses in the Central Nervous System (most are in the spine).
Efferent pathway (motor neuron): conducts impulses from Central Nervous System to effector.
Effector: muscle fibers or glands that respond by contracting or secreting chemicals.
PRO TIP: Spinal reflexes are initiated and completed at the spinal cord level. They occur without the involvement of higher brain centres.
Division of the Nervous System
The Nervous System is divided into two:
- Central Nervous System - Brain and Spinal Cord.
- Peripheral Nervous System - Nerves and Sensory organs.
Central Nervous System
The Central Nervous System consists of the Brain and the Spinal column. It is the main centre of information processing in the entire body.
Brain
Brain is a delicate nervous tissue, located in the head region of animals. It is the seat of consciousness, logical processing, thinking and learning. It is one of the largest organs in the body and it requires constant blood supply.
Every second, millions of chemical and electrical signals pass around the brain and the body’s nervous system.
The brain is shielded by 3 protective membranes (called meninges) that envelop it.
These 3 meninges are:
- Dura mater: this is the outermost layer and it is very tough.
- Arachnoid layer: this is the middle layer and adheres to the dura mater and has weblike attachments to the innermost layer, the pia mater.
- Pia mater: this is the innermost layer and is very thin, transparent, but tough, and covers the entire brain.
Ventricles (chambers) in the brain (specifically lined with clusters of thin walled capillaries called Choroid Plexuses) produce a watery fluid within the skull of higher animals known as cerebrospinal fluid (CSF).
Cerebrospinal fluid is clear liquid that buffers (maintain acid–base level), nourishes, and detoxifies the brain and spinal cord. It flows through the subarachnoid space (between the Arachnoid mater and the Pia mater) and is renewed around four to five times a day.
Brain has 4 main regions:
- Cerebrum
- Cerebellum
- Diencephalon
- Brain Stem
Cerebrum
Cerebrum is the largest, very visible, spaghetti-like portion of the brain.
It is what some people refer to as gray matter — (white matter is buried deep in the brain, while gray matter is mostly found on the brain's surface, or cortex. The spinal cord, which transmits nerve impulses to and from the rest of the body, has the opposite arrangement: gray matter at its core with insulating white matter on the outside).
Cerebrum is the largest portion of the human brain as it encompasses about two-thirds of the brain mass.
It consists of two hemispheres divided by a fissure (called corpus callosum).
The cerebrum includes:
- Cerebral cortex
- Medullary body
- Basal ganglia
Cerebral cortex
Cerebral cortex is a thin layer of tissue which consists mainly of neuron cell bodies, and its folds and fissures (known as gyri and sulci) give the cerebrum its trademark rumpled surface.
The Cerebral cortex is the outermost and exact layer of the brain that is often referred to as gray matter.
The cerebral cortex is gray because nerves in this area lack white fatty myelin sheath. It is this sheath that makes most other parts of the brain appear to be white.
The cortex also consists of folded bulges called gyri that create deep furrows or fissures called sulci.
The folds in the brain add to its surface area which increases the amount of gray matter and the quantity of information that can be processed.
Medullary body
Medullary body is the inner white matter of the cerebrum. I believe you know why it's white - presence of myelin on the axon of its neurons.
Basal Ganglia
Basal ganglia or Basal nuclei are masses of gray matter in each hemisphere which are involved in the control of voluntary muscle movements.
Lobes of the Cerebrum
Cerebrum has 4 important lobes or regions, named after the bones they lie under:
Frontal lobes – (2, one for each hemisphere) – Region for control of personality, voluntary movement.
Parietal lobe – (2, one for each hemisphere) – Region for control of sensory processing and touch, attention.
Temporal lobe – (2, one for each hemisphere) – Region for control of auditory perception, speech, and complex visual perceptions.
Occipital lobe – visual center – plays a role in processing visual information.
In summary, the cerebrum is the Seat of Consciousness and high Intellectual Functions and it is not found in all animals.
Cerebellum
It sits below the posterior (occipital) lobes of the cerebrum and behind the brain stem, as part of the hindbrain.
Like the cerebrum, the cerebellum has left and right hemispheres. A middle region (called vermis) connects them.
The primary function of the cerebellum is to maintain posture and balance. When we jump to the side, reach forward, or turn suddenly, it subconsciously evaluates each movement.
The cerebellum then sends signals to the cerebrum, indicating muscle movements that will adjust our position to keep us steady.
In short, cerebellum fine-tunes body movements and maintains balance.
Cerebellum functions is inhibited by Alcohol.
Diencephalon
This is the region of the brain between the brain stem and cerebrum. It comprises 3 main components:
Thalamus
Epithalamus
This is a small area superior and posterior to (behind) the thalamus.
It consists of a few small nuclei involved in emotional response to odors – also includes the pineal body which is an endocrine gland that may influence the onset of puberty and play a role in controlling long-term cycles that are influenced by day and night.
Hypothalamus
Brain Stem
The brain stem connects the spinal cord to the higher-thinking centres of the brain.
It consists of three structures:
- Medulla oblongata
- Pons
- Midbrain
The medulla oblongata is continuous with the spinal cord and connects to the pons above. Both the medulla and the pons are considered as part of the hindbrain.
The Brain Stem primary function is to relay signals between the Brain and Spinal Cord, and to manage Basic Involuntary Functions.
Pons helps to control breathing rhythms.
Medulla handles respiration, digestion, circulation, and reflexes such as swallowing, coughing, and sneezing.
The midbrain contributes to motor control, vision, and hearing, as well as vision– and hearing–related reflexes.
Brain Waves
Brain waves are rhythmic fluctuation of electric potential between parts of the brain as seen on an electroencephalogram (EEG).
To measure brain waves, electrodes are placed onto the scalp using the EEG.
There are five types of brainwaves:
- Beta: 15 - 30 Hz | Awake or normal alert consciousness.
- Alpha: 9 - 14 Hz | Relaxed, calm meditation.
- Theta: 4 - 8 Hz | Deep meditation and relaxation.
- Delta: 1 - 3 Hz | Deep, dreamless sleep.
- Gamma: 30 Hz + | Highly alert and conscious, peak concentration.
Spinal Cord
It is subdivided into cervical, thoracic, lumbar, sacral and caudal regions.
Its length varies in different animals.
The spinal cord is the main pathway for information, connecting the brain and peripheral nervous system.
Peripheral Nervous System
Peripheral nervous system consists of Nerves (either attached to the brain or the spinal column) and sensory organs. Peripheral Nervous System is subdivided into two systems:
- Somatic Nervous System (Voluntary – involving the senses)
- Autonomic Nervous System (Involuntary – does not require involvement of the senses)
Somatic Nervous System
Somatic Nervous System is responsible for carrying information from the skin, sense organs and skeletal structures to the Central Nervous System, and relaying responses back to skeletal muscles for voluntary response.
You standing up to go and take meat from the pot when you see that everyone is asleep is governed by somatic nervous system.
Autonomic Nervous System
Autonomic Nervous system regulates the body's involuntary responses like breathing, pumping of the heart, the body maintaining internal balance.
The autonomic nervous system is responsible for relay of information to internal organs.
Autonomic Nervous System is subdivided into two divisions:
Sympathetic Nervous System
This part of the autonomic nervous system is engaged during times of stress or emergency response. Example is when a bulldog starts charging towards you, or your phone drops from the top of a 3 storey building.
Parasympathetic Nervous System
This part of the autonomic nervous system involves daily basic activities when the body is at rest or with normal functions. Example is pumping of the heart, blinking of the eyes.
Some parts of the parasympathetic Nervous system are intertwined with the Somatic Nervous system, and can be engaged with voluntary actions. For example you can decide to hold your breathe or stop blinking your eyes for a few seconds.
Major Sense Organs
Unless you probably didn't go through a Primary education, this shouldn't be new to you.
There are 5 major Sense Organs in higher Animals:
- Eyes
- Ear
- Nose
- Tongue
- Skin
These sense organs are responsible for detecting external stimuli that will be taken up by the sensory neurons.
Eyes
Eyes are organs for sensing light signals. The structures responsible for picking up light and color signals in the eyes are the Rods and Cone cells, found in the Retina of the eyes, and they relay impulses via Optic nerves which carry light stimulus to the brain for interpretation, and activated relays when necessary.
PRO TIP: photo, optic, ocul, are used when the eyes or sight is related
Ears
Ears are organs for sensing sound waves. The cochlea in the ear is responsible for picking up sound waves from the environment, and relaying it to the brain via auditory nerves.
PRO TIP: audi- refers to hearing related
Tongue
The mouth contains around 10,000 taste buds, most of which are located on and around the tiny bumps on the tongue. Every taste bud detects five primary tastes:
- Sour.
- Sweet.
- Bitter.
- Salty.
- Umami - salts of certain acids (for example monosodium glutamate/MSG).
Nose
Nose is organ for sensing odours.
Tiny hairs, made of nerve fibers, dangle from all olfactory receptors. They are covered with layer of mucus.
Smell is primarily as a result of chemicals from substances that are suspended in air. If chemicals in air, dissolve in nasal mucus, hairs absorb it and excite the olfactory receptors.
A few molecules are enough to activate these extremely sensitive receptors.
Olfactory Hairs can easily get fatigued so that one does not notice smells.
Smells leave long-lasting impressions, and are strongly linked to memories.
Smell and taste are some kind of intertwined. For instance, I can recall when I was younger, and I would need to drink bitter herbs, I usually don't have a problem with that because all that I need to do, is to hold my nose tightly together and drink the herb. I don't feel a taste. I still practise it till now and other people say it works so I believe its general and not a disorder.
PRO TIP: Olfactory - related to smell.
Skin
Skin is the largest sense organ in an organism and it contain millions of sensory receptors.
Most of the receptors sit close to the skin's surface.
Skin can sense:
- Light touch
- Heavy pressure
- Pain
- Temperature
PRO TIP: derm - skin related
Disorders of the Nervous System
Epilepsy: chronic neurological disorders characterized by seizures.
Seizures: the physical changes in behavior that occur after an abnormal electrical activity in the brain.
Alzheimer’s Disease: degeneration of the brain - causes dementia, which is a gradual loss of memory, judgment, and ability to function - found in 1 out of 10 people over age 65.
Multiple Sclerosis: autoimmune disease that affects the brain and spinal cord (central nervous system) - body's immune system eats away at the protective myelin sheath that covers the axons of the neurons and interferes with the communication - Multiple sclerosis can affect vision, sensation, coordination, movement, and bladder and bowel control.
Parkinson’s Disease: disorder of the brain that leads to shaking and difficulty with walking, movement, and coordination. People with Parkinson's disease have low brain dopamine concentrations.
Shingles (herpes zoster): painful, blistering skin rash due to the varicella-zoster virus, the virus that causes chickenpox – the virus remains inactive (becomes dormant) in certain nerves in the body. Shingles occurs after the virus becomes active again.
Cerebral Palsy: group of disorders that can involve brain and nervous system functions such as movement, learning, hearing, seeing, and thinking resulting from damage to certain parts of the developing brain.
Glaucoma: a group of eye conditions that lead to damage to the optic nerve due to increased pressure in the eye - the eye’s drainage system becomes clogged so the intraocular fluid cannot drain and as the fluid builds up, it causes pressure to build within the eye. High pressure damages the sensitive optic nerve.
Pink eye (Conjunctivitis) – infection of the conjunctiva of the eye.
Meningitis – inflammation of the meninges.
Effect of drugs on the Nervous System
Alcohol: central nervous system depressant – alcohol can easily pass through cell membranes. Once in the bloodstream it can diffuse into almost all body tissues. It is absorbed in the stomach so it gets into the blood stream quickly and slows down function of the nervous system.
Caffeine: acts as a central nervous system stimulant - caffeine suppresses melatonin for up to 10 hours and also promotes adrenalin. Melatonin is strongly associated with quality sleep, while adrenalin is the neurotransmitter associated with alertness.
Nicotine: small doses of nicotine have a stimulating action on the central nervous system – it is highly addictive. Nicotine's effects on the brain cause an increased release of neurotransmitters associated with pleasure. The brain quickly adjusts to repeated nicotine consumption by decreasing the amount of neurotransmitters released. The effect of this increased tolerance is that the smoker must continue to use nicotine in order to avoid the feelings of discomfort associated with withdrawal from the drug. Irritability and anxiety often ensue during nicotine withdrawal.
Marijuana: THC, the main active ingredient in marijuana, binds to membranes of nerve cells in the central nervous system that have protein receptors. After binding to nerve cells, THC initiates a chemical reaction that produces the various effects of marijuana use. One of the effects is suppression of memory and learning centres (called the hippocampus) in the brain.
Summary
♨️The Nervous system is a delicate network of nerves and fibers connected to a Processor that controls all body activities of an organism.
♨️The nervous system is divided into Central Nervous System and peripheral nervous system.
♨️The central nervous system involves the main information processing points while the peripheral nervous system involves all nerves and sensory organs around the body.
♨️Neuron is the structural unit of a nervous system.
♨️Neuron transmit impulses in the form of electrical signals and chemicals.
♨️Transfer of impulse from a neuron to another through a gap junction is called synapsis.
♨️Chemicals used during synapsis through which impulse is transferred from a neuron to another are called neurotransmitters.
♨️Sensory neuron or afferent nerves take stimuli from the environment to the Central Nervous System.
♨️Interneuron or relay neurons bridge the afferent nerves and efferent nerves.
♨️Motor neuron or efferent nerves receive information from the central Nervous system and carry it to effectors through which an action is carried out.
♨️Information pass through a neuron from a dendrite to the cell body to the axon.
♨️The central Nervous system has 2 major components: Brain and Spinal Cord.
♨️The Brain has 4 major regions:
- Cerebrum
- Cerebellum
- Diencephalon
- Brain Stem
♨️The Brain Stem connect the brain to the spinal cord.
♨️The peripheral nervous system is divided into somatic nervous system which involves voluntary actions and autonomic nervous system which involves involuntary actions.
♨️The autonomic nervous system is further divided into sympathetic Nervous system which involves involuntary actions during quick and emergency response and the parasympathetic Nervous system which involves normal body involuntary actions during normal conditions.
♨️The major sensory organs in the somatic nervous system are eyes, nose, ears, tongue and skin.
Key Terms
• Nervous System • Neurons • Dendrites • Soma • Axon • Schwann cells • Glial cells • Myelin sheath • Node of Ranvier • Afferent nerves •Efferent nerves • Impulses • Synapse • Neurotransmitters • Meninges • Dura mater • Arachnoid layer • Pia mater • Choroid Plexus • Cerebrospinal fluid • Cerebrum • Gray matter • Corpus callosum • Cerebral cortex • Gyri • Sulci • Medullary body • Basal ganglia • Frontal Lobe • Parietal Lobe • Temporal Lobe • Occipital Lobe • Broca’s area • Wernicke’s area • Cerebellum • Vermis • Diencephalon • Thalamus • Epithalamus • Hypothalamus • Brain Stem • Medulla Oblongata • Pons • MidBrain • Electroencephalogram • Spinal Cord • Peripheral Nervous System • Somatic Nervous System • Autonomic Nervous System • Sympathetic Nervous System • Parasympathetic Nervous System • Effectors
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TEST QUESTIONS: NERVOUS SYSTEM
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TEST QUESTIONS: NERVOUS SYSTEM
Total Questions: 45
you'll have 28 second to answer each question.
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Quiz Answers
1. The direction of impulse transmission in a neuron is as shown in one of the following
Dendrites - Cell body - Axon - Synapse
2. The protective sheath on the axon is...
Myelin
3. The brain stem is divided into _ sections
3
4. Afferent and Efferent fibers means _ and _ respectively
Inflowing and Outflowing
5. The structural unit of the nervous system is...
Neuron
6. _ receive impulse signals into a neuron
Dendrite
7. Myelin sheath form a protective layer of coating on...
Axon
8. Glial cells are part of the nervous system
False
9. Myelin is produced by glial cells in a process called...
Myelination
10. Small gaps between myelin sheaths on the axon is known as...
Node of Ranvier
11. Myelinated neurons are faster in conducting electrical signals as it moves through the nervous system
True
12. _ neurons bring signals from sense organs to the CNS
Sensory neuron
13. _ neurons carry messages from the CNS to the effectors for appropriate action
Motor neuron
14. _ is a change in environment capable of initiating a response
Stimulus
15. The ability of a neuron to respond to stimulus and convert it into a nerve impulse is termed...
Excitability
16. Transfer of impulse between two neurons is known as...
Synapsis
17. Signal is transmitted between two neurons in synapsis with the aid of a chemical messenger called...
Neurotransmitters
18. _ is a type of neurotransmitter that discourages chemical signals and cellular responses in other neurons
Inhibitory neurotransmitter
19. _ is the simplest neural pathway by which a reflex occur
Reflex arc
20. Effectors are muscle fibers or glands that ...
Respond to nervous signals
21. The brain is shielded by 3 protective membranes called _
Meninges
22. One of these is not a part of the meninges of the brain and spinal cord
Choroid plexus
23. Cerebrospinal fluid is a watery fluid that cushions the brain and spinal cord and is produced in...
Choroid plexus
24. The Largest part of a human brain is...
Cerebrum
25. _ is referred to as grey matter
Cerebrum
26. Cerebrum appears to be grey-like in colour, which of the options best explains this?
Absence of myelin sheaths on the neurons of the outer covering of the cerebrum is the reason for grey colour
27. The folded bulges of the human cerebral cortex is called _ and these create deep furrows or fissures in the cortex called _
Gyri, sulci
28. _ lobe in the cerebrum is responsible for processing visual information
Occipital
29. _ lobe in the cerebrum is responsible for judgements, control of personality
Frontal
30. _ lobe in the cerebrum is responsible for auditory perception, speech and complex visual perception
Temporal
31. _ lobe in the cerebrum is responsible for sensory perception like touch and feel etc
Parietal
32. Cerebellum has left and right hemispheres that is connected by a middle region called _
Vermis
33. The seat of consciousness and high intellectual functions in the brain is...
Cerebrum
34. The primary function of _ is to maintain posture and balance
Cerebellum
35. One of these is not a component of the diencephalon
Pons
36. Many basic involuntary actions are controlled by the _
Brain stem
37. Rhythmic fluctuation of electric potential between parts of the brain can be recorded by...
Electroencephalogram
38. The main information pathway connecting the brain and the peripheral nervous system is...
Spinal cord
39. The voluntary PNS is known as
Somatic NS
40. _ controls involuntary actions and maintains internal balance within the body
Autonomic Nervous System
41. Response in time of emergency is controlled by which type of autonomic nervous system?
Sympathetic Nervous System
42. One of these is not a sense organ
Teeth
43. Inflammation of the meninges is termed...
Meningitis
44. _ connects the nervous system to the endocrine system
Hypothalamus
45. _ connects the brain to the spinal cord
Brain stem
Discuss and Explain
1. Jane was baking cupcakes for her friend’s birthday on the weekend. She was distracted talking to her mother and picked up a hot tray. Before Jane had time to think about what she was doing, she had dropped the tray. Explain how Jane was able to react so quickly.
2. John has been bullied by people at school for a while. As soon as John sees the bullies, his heart starts to race, his pupils dilate and he feels the need to urinate. Identify which system is responsible for this reaction.
3. Describe the two functions of the peripheral nervous system.
4. Dave has been outside for the last three hours. As the sun begins to set, Dave realises it is getting colder. Identify:
a) the neuron responsible for alerting Dave to this.
b) which part of the parasympathetic nervous system will be active to relieve this feeling.
5. Compare the central nervous system with the peripheral nervous system.
6. Differentiate between sensory neuron, motor neuron and interneurons.
7. Communication between neurons can be interrupted by substances, such as alcohol and pain relief medication. Consider the implications of disrupting neuron communication. In your response, acknowledge the advantages and disadvantages.
8. People often emphasise the importance of the sympathetic nervous system as the only survival system. Consider what may happen if the parasympathetic nervous system were malfunctioning.
