nervous system Flashcards
how does the nervous system function in response to a stimulus?
-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
what are axons?
-carry impulses away from the cell body
what are dendrons?
-carry impulses towards the cell body
-dendrites receive nerve impulses from other neurones
what is the myelin sheath?
-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
what are sensory neurones?
-transmit nerve impulses from the receptors to the central nervous system
what are motor neurones?
-transmit nerve impulses from the central nervous system to the effectors
what are relay neurones?
-relay impulses from sensory neurone to motor neurone inside the central nervous system
-located in the central nervous system
what is a synapse?
-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
structure of the spinal cord
-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
what is the dorsal root?
-contains only sensory neurones
-cell bodies of the sensory neurones clustered in dorsal root ganglion
what is the ventral root?
-contains only motor neurones
-the cell bodies and dendrons of the motor neurone lie in the grey matter of the spinal cord
what is the pathway of nerve impulses of voluntary actions?
-brain —> relay neurone in spinal cord —> motor neurone —> effector
what is a reflex action?
-a reflex action is an automatic response to a specific stimulus without any conscious control
what is a spinal reflex?
-when the spinal cord is the reflex centre of the reflex action
-withdrawal of hand when the person touches a hot pan, knee jerk
what is a cranial reflex?
-when the brain is the reflex centre of the reflex action
-a person sees a swinging bat approaching and blinks, pupil reflex
what is the reflex arc?
-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
withdrawal of hand from a hot pan
-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.
when a person enters a bright room from a dimly lit room
-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
reflex action vs voluntary action
-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
nervous vs endocrine system
-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
