Topic 9 Nervous System Flashcards
What is part of the central nervous system?
brain and spinal cord and linked to sense organs by nerves
What is a neurone?
Nerve cell
Many neurones make a nerve
What is a sensory neurone?
Transfers nerve impulses from receptors to CNS
What is a relay neurone?
In the CNS, transmits nerve impulses from sensory neurone to motor neurone
What is a motor neurone?
Sends nerve impulse from CNS to effector (eg muscle or gland)
What is the function of the cell body?
Contains nucleus
What is the function of the dendrons/dendrites?
Extensions of cell body which carries nerve impulses towards the cell body
What is the function of the axon?
Carries nerve impulses away from the cell body
What is the function of the myelin sheath?
Fatty material which insulates cell extensions + speeds rate of transmission of electrical impulses
What is the receptor?
- receptor cell in sense organ detects change + generates nerve impulse -> passes along a sensory neurone into CNS
What is the coordinator?
Relay neurones take impulse through spine, brain and transmit to correct neurone
What is the effector?
Motor neurone takes impulse out of CNS to correct effector organ (muscles)
What is the response?
A reaction that happens eg muscle contraction
What is a reflex action?
An involuntary action
Happens automatically + rapidly in response to stimuli
What are the characteristics of a reflex action?
- helps protect body from damage
- brings about a rapid response by involving few neurones, so few synapses
- involves brain + spinal cord but not conscious thought
What is the nerve pathway for a voluntary action?
Receptor senses stimuli from surroundings
Sensory neurone -> relay neurone in spinal cord
Brain receives impulses from spinal cord + sends out new impulses -> motor neurone -> effector
What is the nerve pathway for involuntary action?
Receptor senses stimuli from surroundings
Sensory neurone -> relay neurone -> motor neurone -> effector
What is a synapse?
Gap between two neurones (needs to be crossed to or from CNS)
How is a synapse crossed?
- Electrical signal travels along axon + triggers neurotransmitters in nerve ending of neurone 1 to be released
- These diffuse across gap and stimulate neurone 2 to re transmit electrical impulse (they attach to membrane of 2nd neurone)
Broken down by enzyme once impulse has been transmitted
What are the differences between the nervous and endocrine systems?
- signal carried by…
- type of signal….
- speed of signal…
- signal carried in…
- area of response…
- duration of message…
N: signal carried by neurones, E: hormones
N: electrical signal, E: chemical signal
N: fast, E: slow
N: signal carried in neurones, E: blood
N: area of response localised, E: widespread
N: duration of message short E: long
What is the function of the cornea?
Refracts light as it enters eye
What is the function of the iris.
Controls how much light enters the eye
What is the function of the pupil?
Allows light to enter eye
What is the function of the lense?
Refracts light to focus onto retina
What is the function of the ciliary muscles?
Adjust shape of lense to make it more or less curved
This increases/decreases refraction of light
What is the function of the suspenders ligaments?
Slacken or stretch as ciliary muscles contract or relax to adjust thickness / curvature of lens
What is the function of the retina?
Contains light receptors which trigger electrical impulses to send to brain when light is detected
Contains light receptors rods (sensitive to dim light, black and white) cones (colour)
What happens to the eye in bright light?
- Circular muscles contract
- Radial muscles relax
- Pupil constricts
What happens to the eye in dim light?
- Circular muscles relax
- Radial muscles contract
- Pupil dilates
What happens when focusing on a distant object? (Accommodation reflex)
- Ciliary muscles relax
- Suspenseful ligaments pulled tight
- Lens flat
- Less refraction
What happens when focusing on a nearby object?
- Ciliary muscles contract
- Suspenders ligaments are slack
- Lens -> more rounded
- More refraction
