Nervous system pt. II Flashcards
Name the three different types of neurons and state their functions.
Sensory neuron – transmits impulses from receptor to the CNS.
Relay neuron – transmits impulses from sensory neuron to motor neuron.
Motor neuron – transmits impulses from CNS to effector.
State the locations at which the different neurons are found.
Motor neuron – in the PNS, between CNS and effector organ.
Sensory neuron – in the PNS, between CNS and sense organ.
Relay neuron – in the CNS, connecting the sensory and motor neurons.
Distinguish between the appearances of the motor neuron and sensory neuron.
Motor neuron is a single, long axon and has several short dendrons projecting from the cell body. The cell body is at one end of the neuron.
Sensory neuron has long dendron and short axon. The cell body is not at one end of the neuron but in between the axon and dendron.
State what the white matter and grey matter mainly consist of, and where they are located in the brain and spinal cord.
White matter consists of mainly cell fibers.
Grey matter consists of mainly cell bodies.
In the brain, the grey matter is on the surface while white matter is in inner layer.
In the spinal cord, white matter is on the outside while grey matter is inside.
State the two roots the spinal nerve bifurcates into and the type(s) of neurons inside this root.
Ventral root, front of body, contains only motor neurons. [VFM]
Dorsal root, back of body, contains only sensory neurons. [DBS]
State the function of the dorsal root ganglion.
It is a small swelling that allows cell bodies of sensory neurons to be aggregated.
State the function of the spinal cord.
The spinal cord acts as the pathway for nerve impulses into the brain from the receptor and out of the brain to the effector. It acts as the coordinator for simple reflex action.
Define a reflex action and state its purpose.
A spontaneous response to a specific stimulus without conscious control. It is the most basic form of response in higher animals to protect them from harm and injury.
Define the reflex arc and state what it comprises.
It is the shortest pathway by which impulses travel from receptor to effector in reflex action. It comprises the receptor, neurons, spinal cord and / or brain and effector.
Outline the reflex arc of touching a hot object.
- Heat stimulates nerve endings (receptors) in the skin that initiate nerve impulses.
- Nervous impulses travel along dendron of sensory neuron to spinal cord.
- In the spinal cord, impulses are transmitted across synapse to relay neuron.
- Impulses transmitted across another synapse to motor neuron.
- Travel along axon of motor neuron to effector.
- Biceps muscle (effector) contracts to bring about sudden withdrawal of hand (response).
Describe a conditioned reflex action.
It is a reflex action acquired from past experience. The stimulus was originally ineffective in producing response.
