nervous system

Question 1

define sensitivity

Answer 1

the ability to respond to a stimulus

Question 2

state the 2 main parts of nervous system

Answer 2

• central nervous system (brain + spinal cord)
• peripheral nervous system (cranial nerves, spinal nerves, sense organs)

Question 3

briefly describe what the nervous system does

Answer 3

collects information about external and internal environment, processes and integrates the information, initiates an appropriate response to the stimulus, thereby coordinating the organism’s activity

Question 4

briefly describe how the parts of nervous system work together (general)

Answer 4

1. receptors in sense organs detect stimuli and generate nerve impulses
2. these nerve impulses are transmitted by nerves to the CNS
3. the CNS receive information from receptors, integrate and intepret the information, initiating a response
4. nerve impulses are then rapidly transmitted by nerves to the appropriate effectors, which are either muscles or glands, for the response to be carried out

Question 5

what do neurones consist of?

Answer 5

a cell body and a number of nerve fibres

Question 6

state the direction of nerve impulse transmission in sensory, motor, and relay neurones.

Answer 6

• sensory: from receptors to CNS
• relay: from sensory neurone to motor nerone inside the CNS
• motor: from CNS to effectors

Question 7

fill in the blanks in this diagram

Answer 7

answer

Question 8

contrast axons and dendrons

Answer 8

• axon: transmits impulses away from cell body
• dendron: transmits impulses toward cell body

Question 9

state the parts of a motor neurone

Answer 9

• cell body
• nerve fibres: dendrons and axons
• myelin sheath consists of Schwann cells wrapped around the axon
• in between two Schwann cells is the node of Ranvier

Question 10

describe Schwann cells, and its function

Answer 10

Schwann cells wrap around axons and dendrons of many neurones at regular intervals
the membranes of Schwann cells form the myelin sheath, which is located outside plasma membrane of the axon

functions of myelin sheath:
* prevents the loss of current in the form of Na+ and K+ from the axon
* which increases the speed of transmission of nerve impulses along the axon
* myelinated neurones hence transmit impulses faster than non-myelinated neurones

gaps between Schwann cells where myelin sheath is absent are Nodes of Ranvier

Question 11

describe synaptic knobs and their function

Answer 11

bulbous structures at the end of axons

they relay nerve impulse from one neurone to another through the release of chemicals called neurotransmitters, which are contained in vesciles known as synaptic vesicles

Question 11

contrast cranial and spinal nerves

Answer 11

cranial: from the brain
spinal: from spinal cord

Question 11

describe dorsal roots and ventral roots outside spinal cord

Answer 11

• each segment of spinal cord is associated with a pair of ganglia, called dorsal root ganglia
• these ganglia contain cell bodies of sensory neurones, and the axons of these sensory neurones travel into spinal cord via dorsal roots
• ventral roots consists of axons from motor neurones, which bring information to the periphery from cell bodies within the CNS
• dorsal and ventral roots come together and become spinal nerves

Question 12

define voluntary action

Answer 12

an action under control of a will

Question 12

contrast grey matter and white matter

Answer 12

grey metter: consists mainly cell bodies of neurones
* outer layers of the brain
* central parts of spinal cord

white matter: consists mainly of nerve fibres
* central parts of brain
* outer layers of spinal cord

position of grey and white matter in brain and spinal cord is opposite

Question 13

contrast spinal reflexes and cranial reflexes

Answer 13

• spinal: controlled by spinal cord
• cranial: controlled by brain, and usually occurs within head region

Question 13

define reflex action

Answer 13

immediate response to a specific stimulus without conscious control

Question 14

define reflex arc

Answer 14

the shortest pathway by which nerve impulses travel from the receptor to the effector in a reflex action

Question 15

describe the nervous pathway for the reflex of withdrawing hand from a hot pan

Answer 15

1. heat from pan stimulates temperature receptors in the skin which generate nerve impulses that are transmitted along sensory neurone to the spinal cord
2. in the spinal cord, the impulses are transmitted across a synapse to the relay neurone and across another synapse to the motor neurone
3. (when nerve impulses from receptors arrive at spinal cord, relay neurone also transmits nerve impulses to the brain to make the brain aware of what is happening)
4. nerve impulses are transmitted across synapses by release of neurotransmitters
5. nerve impulses leave the spinal cord along the motor neurone to the bicep muscles, which contract to bring out the sudden and immediate withdrawal of hand

point 3 is depending on question

Question 16

contrast reflex and voluntary actions (at least 2 points)

Answer 16

reflex vs voluntary
* does not involve vs involves conscious control
* stimulus is always vs not always involved
* occurs faster vs slower
* the same stimulus will always vs may not always result in the same result

Question 17

contrast nervous and endocrine system (at least 3 points)

Answer 17

nervous vs endocrine
1. involves nerve impulses and chemicals vs hormones
2. impulses are transmitted by neurones vs hormones are transmitted by blood
3. usually quicker vs shorter responses
4. responses are short-lived vs short or long-lived
5. may be voluntary or involuntary vs always involuntary
6. usually localised vs usually affects one or more target organs