Question

1)Name two differences between the parasympathetic and sympathetic nervous systems.

2)Describe six steps of transmission at a neuron to neuron synapse using the illustration below.

3)Name two functions of cerebrospinal fluid.

4)Describe a somatic reflex

Answer 1

1)

• Sympathetic system is controlled by thoraco-lumbar vertebrae (T1,2 - L1,3) Whereas parasympathetic system is controlled by cranio-sacral vertebrae; Cranial nerve III, VII, IX, X
• Sympathetic system controls the 'Fight and flight ' condition Rest & Digestion control is undertaken by parasympathetic system
• Adrenoreceptors are involved (Alpha & Beta receptors) Cholinoreceptors are involved in Parasympathetic system (Muscarinic & Nicotinic receptors)

2)

Step 1: Presynaptic neuron is excited by an electrical signal called 'Action potential'

Step 2:Calcium ions enters to the presynaptic terminal & Vesicles containing the neurotransmitter moves towards the plasma membrane of presynaptic membrane and fuse with it & Relaese of the neurotransmitter into the synaptic cleft.

Step 3: Interaction of neurotransmitter with the receptor proteins present on the postsynaptic neuron & Na+ ion channels in the postsynaptic membrane open and Na+ ions diffuse into the postsynaptic neuron

Step 4:  A threashold potential is created in the postsynaptic neuron and thus the action potential begins.

Step 5: The neurotransmitter is degraded by specific enzymes released from the receptor proteins.

Step 6: Na+ ion channels closes, no further Na+ ions can diffuse into the postsynaptic neuron.

3)

1. CSF provides nutrients to the nervous system tissues and flushes away the metabolic waste products from it.
2. Act as a cushion around the brain and spinal cord to protects from a sudden shock or trauma.

4)

Patellar reflex is an example for Somatic Motor reflex:

• The sensory receptor responds to the stimulus by producing a generator or receptor potential.------------The tendon of the knee is stretched by tapping at the knee resulting in stretching of the quadriceps muscle spindle
• The sensory neuron conducts impulse from the receptor to the integrating centre.---------------------------Sensory neuron carries the information
• The integrating centre is one or more regions within the CNS that relay impulses from sensory to motor neuron.------------------------------Enters the Spinal cord via dorsal root and synapse with the interneuron which transfers the signal to the motor neuron to cause motor neuron activation.
• Motor neuron axon conducts impulse from the integrating centre to the effector organ.----------------------------Motor neuron exit with the signal through the ventral root
• Effector muscle that respond to the motor nerve impulse.--------------------------------------------------Muscle contraction occurs to retreive the knee.