nervous system

Question 1

how does the nervous system function in response to a stimulus?

Answer 1

-receptors receive stimuli and generate nerve impulses
-nerve impulses are then transmitted to the CNS by the peripheral nerves along the sensory neurones
-brain and spinal cord interprets information and initiates a response
-a nerve impulses is then transmitted to the effector via the peripheral nerves along the motor neurone

Question 2

what are axons?

Answer 2

-carry impulses away from the cell body

Question 3

what are dendrons?

Answer 3

-carry impulses towards the cell body
-dendrites receive nerve impulses from other neurones

Question 4

what is the myelin sheath?

Answer 4

-made up of schwann cells
-protect and insulate the axons and dendrons to enhance speed of nerve impulse transmission
-nerve ‘jump’ from one node of ranvier to the next between the myelin sheath, speeding up transmission

Question 5

what are sensory neurones?

Answer 5

-transmit nerve impulses from the receptors to the central nervous system

Question 6

what are motor neurones?

Answer 6

-transmit nerve impulses from the central nervous system to the effectors

Question 7

what are relay neurones?

Answer 7

-relay impulses from sensory neurone to motor neurone inside the central nervous system
-located in the central nervous system

Question 8

what is a synapse?

Answer 8

-a gap between one neurone and the next or between a neurone and an effector
-nerve impulses are transported across the synapse by neurotransmitters
-neurotransmitters bind to receptors on the dendrite of the following neurone which triggers a nerve impulse

Question 9

structure of the spinal cord

Answer 9

-the spinal cord is protected by the backbone, that consists of
-outer part of white matter and inner H-shape of grey matter
-central canal filled with fluid called cerebrospinal fluid which nourishes the spinal cord
-dorsal and ventral root

Question 10

what is the dorsal root?

Answer 10

-contains only sensory neurones
-cell bodies of the sensory neurones clustered in dorsal root ganglion

Question 11

what is the ventral root?

Answer 11

-contains only motor neurones
-the cell bodies and dendrons of the motor neurone lie in the grey matter of the spinal cord

Question 12

what is the pathway of nerve impulses of voluntary actions?

Answer 12

-brain —> relay neurone in spinal cord —> motor neurone —> effector

Question 13

what is a reflex action?

Answer 13

-a reflex action is an automatic response to a specific stimulus without any conscious control

Question 14

what is a spinal reflex?

Answer 14

-when the spinal cord is the reflex centre of the reflex action
-withdrawal of hand when the person touches a hot pan, knee jerk

Question 15

what is a cranial reflex?

Answer 15

-when the brain is the reflex centre of the reflex action
-a person sees a swinging bat approaching and blinks, pupil reflex

Question 16

what is the reflex arc?

Answer 16

-the reflex arc is the shortest pathway by which nerve impulses travel from the receptors to the effector in a reflex action
-receptor —> sensory neurone —> reflex centre at spinal cord/ brain —> relay neurone —> motor neurone —> effector

Question 17

withdrawal of hand from a hot pan

Answer 17

-heat from the pan stimulates temperature receptors in the skin
-nerve impulses are generated by the receptor, which are transmitted along the sensory neurone to the spinal cord
-in the spinal cord, the impulses are transmitted across a synapse to the relay neurone and then across another synapse to the motor neurone
-the nerve impulses are transmitted across the synapses by the release of neurotransmitters
-nerve impulses leave the spinal cord along the motor neurone to the bicep muscles/ effector
-the bicep muscles contract, to bring out the sudden and immediate withdrawal of the hand
-when the nerve impulses from the receptors arrive at the spinal cord, the relay neurone also transmits the nerve impulses to the brain. this makes the brain aware of what is happening.

Question 18

when a person enters a bright room from a dimly lit room

Answer 18

-when the person enters a brightly lit room, light from the surroundings enters the eye
-bright light is detected by the photoreceptors in the retina
-nerve impulses are generated by the photoreceptors, which are transmitted along the sensory neurones/ optic nerve to the brain
-in the brain, the nerve impulses are transmitted across a synapse to the relay neurone and then across another synapse to the motor neurone
-nerve impulses leave the brain along the motor neurone to the circular and radial muscles of the iris/ effector
-the circular muscles of the iris contracts, and the radial muscles of the iris relax

Question 19

reflex action vs voluntary action

Answer 19

-does not involve conscious control vs involves conscious control
-stimulus is always involved vs stimulus may not always be involved
-occurs faster vs occurs slower
-the same stimulus always results in the same response vs the same stimulus may not always result in the same response

Question 20

nervous vs endocrine system

Answer 20

-involves nerve impulses vs involves hormones
-impulses transmitted by neurones vs hormones transmitted by blood
-usually quick responses vs usually slower responses
-responses are short-lived vs responses may be short or long-lived
-may be voluntary or involuntary vs always involuntary
-usually localised vs tend to affect one or more target organs