The Nervous System Flashcards
Relationship between receptors, the central nervous system and the effectors.
Stimuli—>central nervous system—-> effectors
What is reflex arc
A reflex arc is the shortest pathway by which nerve impulses travel from the receptor to the effector in a reflex action.
Function of sensory neurones
Transmits nerves impulses from the sense organs to the central nervous system.
Function of relay neurone
Transmits never implises from the sensory neurone to the motor neurone
Function of motor neurone
Transmits nerve impulses from the central nervous system to the effectors.
Reflex centres
- Cranial reflexes—> controller by the brain( unconsciously)
- Spinal reflexes—> controlled by the spinal cord
What happens when you touch a hot object?
- The heat on the object stimulates the thermal receptors in your skin. Electrical impulses are produced.
- The electrical impulses travel along the sensory neurone to the spinal cord.
- In the spinal cord, the electrical impulses are transmitted first across a synapse to a relay neurone, then across another synapse to the motor neurone.
- The motor neurone transmits the electrical impulses from the spinal cord to the muscle tissues in the affected arm.
- The biceps muscle contract and causes the hand to withdraw suddenly.
Function of iris
Structure: a circular sheet of muscles
Functions:
1. It contains a pigment that gives the eye its colour
2. It controls the amount of light entering the eye with the circular muscles and radial muscles
Function of conjunctiva
Structure: a thin transparent membrane covering the sclera
Function:
1. It secretes mucus to keep the eyeball moist.
Sclera or sclerotic coat
Structure: A tough white outer covering of the eyeball
Function:
1. Protects the eyeball from mechanical injuries.
Pupil
Structure: A hole in the Centre of the iris
Function: allows light to enter the eye.
Eyelashes
Function: shield the eye from dust particles
Eyelids
Functions:
1. Protects the cornea from mechanical injuries.
2.
Tear gland
- Secretes tears—> wash away dust
Ciliary body
- Contains ciliary muscles which control the curvature/thickness of the lens