Ch. 33 - The Nervous System

Question 1

What is the CNS?

Answer 1

The central nervous system consists of the brain and spinal cord.

Question 2

What is the PNS?

Answer 2

The peripheral nervous system carries messages between the CNS and the rest of the body.

Question 3

What is a neuron?

Answer 3

A neuron is a nerve cell.

Question 4

What is a sensory(afferent) neuron?

Answer 4

A sensory neuron takes a message from the sense organ to the CNS.

Question 5

What is a motor(efferent) neuron?

Answer 5

A motor neuron takes a message from the CNS to a muscle or gland.

Question 6

Draw a diagram of a motor and sensory neuron.

Answer 6

Sensory neuron: Has cell body in the middle, impulses go from the PNS to the CNS.
Motor neuron: Has a cell body at the dendrites, impulses go from the CNS to the PNS.
Both neurons: Have dendrites at the beginning and neurotransmitter swellings and axon terminals at the end. Axon/dendrite runs down the middle. Myelin sheath around the dendrite/axon. Schwann cells in the sheath. Node of Ranviers between sheaths.

Question 7

What is the function of the receptor?

Answer 7

The receptor is a cell or group of cells that detect a stimulus.

Question 8

What is the function of the nerve endings?

Answer 8

Nerve endings connect sensory neurons to receptor cells.

Question 9

What are dendrites and axons?

Answer 9

Dendrites are fibres that carry impulses towards the cell body. Axons are fibres that carry impulses away from the cell body.

Question 10

What is the function of the Schwann cell?

Answer 10

Schwann cells produce the myelin sheath.

Question 11

What is the function of the myelin sheath?

Answer 11

The myelin sheath is the fat rich layer that insulates the electrical impulses. They increase the speed of transmission, as the impulse ‘jumps’ from one node of Ranvier to the next.

Question 12

What is the cell body?

Answer 12

The cell body contains a nucleus and organelles. Some contain mitochondria, providing energy for the movement of nerve impulses. They form the dendrites and axons that emerge from it. They form neurotransmitter chemicals.

Question 13

What are axon terminals?

Answer 13

Axon terminals are branches formed by the splitting of an axon. They carry impulses to the neurotransmitter swellings.

Question 14

What are neurotransmitter swellings?

Answer 14

Neurotransmitter swellings release chemicals that carry impulses from one neuron to another. Neurotransmitters are stored in vesicles in the swellings.

Question 15

What is an interneuron?

Answer 15

The interneuron(association neuron) carries information between sensory and motor neurons.

Question 15

What is a resting neuron?

Answer 15

A resting neuron is a neuron that is not carrying any impulse.

Question 15

What is a ganglion?

Answer 15

A ganglion is a group of cell bodies located outside the CNS.

Question 16

Draw a diagram of an interneuron.

Answer 16

Dendrites at the beginning leading up to the cell body in the middle. Then axons lead to the axon terminals and neurotransmitter swellings.

Question 16

What is the threshold?

Answer 16

The threshold is the minimum stimulus needed to cause an impulse to be carried in a neuron.

Question 17

What is the all or nothing law?

Answer 17

The all or nothing law states that if the threshold is reached, an impulse is carried, but if the threshold is not reached, no impulse is carried.

Question 18

What is the refractory period?

Answer 18

The refractory period is a short time span after a neuron has carried an impulse during which a stimulus fails to cause a response.

Question 18

What is a synaptic cleft?

Answer 18

A synaptic cleft is the tiny gap between the 2 neurons at a synapse.

Question 19

How do nerve impulses travel between 2 neurons in close contact?

Answer 19

The impulse arrives at the axon terminal. Neurotransmitters are released, they diffuse across the synaptic cleft and bind to a receptor. This causes an impulse to start in the next neuron. Then enzymes break down the neurotransmitter and it is reabsorbed.

Question 19

What is a synapse?

Answer 19

A synapse is a region where 2 neurons come into close contact.

Question 20

Give examples of neurotransmitters.

Answer 20

Acetylcholine, norepinephrine(noradrenaline) and dopamine.

Question 21

How is the brain and spinal cord protected?

Answer 21

The brain and spinal cord are protected by bone, the cranium and vertebrae respectively. They’re also covered by 3 membranes called meninges. The space between the inner 2 meninges is filled with cerebrospinal fluid. This fluid acts as a shock absorber and an exchange medium between blood and brain.

Question 21

What is the function of the synapse?

Answer 21

Synapses transmit impulses, control the direction of impulse and prevent the overstimulation of effectors.

Question 22

Draw a diagram of the brain.

Answer 22

Diagram pg. 381. Includes cerebrum, thalamus, hypothalamus, meninges, pituitary gland, medulla oblongata, cerebellum and spinal cord.

Question 22

What are the functions of the cerebrum?

Answer 22

The cerebrum controls voluntary movements. It also receives and interprets impulses from sense organs. (Other functions include thinking, intelligence, memory, language, emotions, judgement and personality).

Question 23

What is the function of the cerebellum?

Answer 23

The cerebellum controls muscular coordination and balance. The responses of the cerebellum are involuntary.

Question 24

What is the function of the medulla oblongata?

Answer 24

The medulla oblongata controls involuntary actions such as breathing, blood pressure, swallowing, coughing and sneezing.

Question 25

What is the function of the thalamus?

Answer 25

The thalamus acts as a sorting centre for the brain.

Question 26

What is the function of the hypothalamus?

Answer 26

The hypothalamus regulates body conditions for homeostasis. Monitors blood temperature, pressure, appetite, thirst and osmoregulation. It is linked with the pituitary gland to regulate the production of hormones.

Question 27

What is the function of the pituitary gland?

Answer 27

While the pituitary gland is not a part of the brain, it produces numerous hormones.

Question 28

Parkinson’s disease.
-What is its cause?
-What are the symptoms?
-How is it prevented?
-What treatment is given?

Answer 28

-Parkinson’s is caused by a failure to produce dopamine in a part of the brain.
-Trembling of hands and legs, stiffness, poor balance, unblinking gaze.
-No known method for prevention.
-Physiotherapy.

Question 29

Draw a TS of the spine.

Answer 29

Diagram pg. 383

Question 30

What is a reflex action?

Answer 30

A reflex action is an automatic, involuntary response to a stimulus. Examples include, grasp reflex, blinking, movement of iris, breathing and knee jerk.

Question 31

What is a reflex arc?

Answer 31

A reflex arc is the pathway taken by a nerve impulse in a reflex action.

Question 32

Describe a reflex arc.

Answer 32

A stimulus is detected by a receptor. An impulse is set up at the receptor. The impulse is sent along the sensory neuron. Then it passes to an interneuron. In the CNS it passes to a motor neuron. The motor neuron passes the impulse to an effector muscle and the effector muscle reacts.