To maintain the body's homeostasis, the functions of the organs and organ systems must be coordinated. Coordination is the process through which multiple organs interact and complement each other's functions. For instance, during physical exercise, the demand for energy increases to sustain heightened muscular activity, necessitating an increased supply of oxygen. This increased oxygen supply requires a higher respiration rate, faster heartbeat, and enhanced blood flow through the blood vessels.
The human neural system is categorized into two main parts:
The PNS is divided into two divisions:-
Nervous tissue originates from the ectoderm and is specialized for receiving stimuli (Excitability) and transmitting messages (conductivity).
Neuron (Nerve Cell)
(i) Cell body or Cyton
(ii) Dendrites or dendrons
(iii) Axon
Generation and Conduction of Nerve Impulse (Conduction of Nerve Impulse along the Axon)
It includes the brain and the spinal cord. Approximately 70-80% of brain development occurs by age 2, with complete development achieved by age 6. The spinal cord fully develops between 4 to 5 years of age. The brain is the central information-processing organ of our body, acting as the 'command and control system.'
Brain
(i) Forebrain
(ii) Midbrain
(iii) Hindbrain
(i) Forebrain: The forebrain consists of the cerebrum, thalamus and hypothalamus.
(ii) Midbrain: It is a small part of the brain. The midbrain is located between the forebrain's diencephalon and the hindbrain's pons. A canal called the Cerebral aqueduct/ Aqueduct of Sylvius passes through the midbrain.
(iii) Hindbrain: The hindbrain comprises pons, cerebellum and medulla (also called the medulla oblongata).
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1. Which part of the brain is responsible for coordinating voluntary movements?
(a) Medulla oblongata (b) Hypothalamus
(c) Cerebellum (d) Thalamus
Answer: (c) Cerebellum
2. The gap between two neurons is called:
(a) Synapse (b) Dendrite
(c) Axon (d) Myelin sheath
Answer: (a) Synapse
3. Which of the following neurotransmitters is primarily associated with the sympathetic nervous system?
(a) Acetylcholine (b) Dopamine
(c) Serotonin (d) Norepinephrine
Answer:(d) Norepinephrine
4. Which of the following is NOT a function of the medulla oblongata?
(a) Regulating heart rate (b) Controlling breathing
(c) Coordinating balance and posture (d) Regulating blood pressure
Answer: (c) Coordinating balance and posture
5. The part of the neuron that receives signals from other neurons is called:
(a) Axon (b) Soma
(c) Dendrite (d) Synaptic terminal
Answer: (c) Dendrite
(1) Comparatively more permeable to K+ and impermeable (nearly impermeable) to Na+
(2) Impermeable to negatively charged proteins present in the axoplasm
(3) (1) & (2) both
(4) More permeable to Na+ ions than K+ ion
Answer: (3) (1) & (2) both
(1) Myelinated nerve fibres are found in the spinal and cranial nerve.
(2) Unmyelinated nerve fibre is enclosed by a schwann cell.
(3) In the resting stage the axonal membrane is comparatively more permeable to potassium ion and nearly impermeable to sodium ions.
(4) Axolemma is more permeable to negatively charged proteins present in the axoplasm.
Answer: (4) Axolemma is more permeable to negatively charged proteins present in the axoplasm.
(a) Limbic lobe consists of amygdala and pons.
(b) Cerebral aqueduct passes through the midbrain.
(c) The medulla contains centers which control respiration, cardiovascular reflexes and gastric secretions.
(d) Brain stem forms the connections between the cerebrum and midbrain.
(e) Knee jerk reflex is a polysynaptic reflex. Choose the correct answer from options given below :
(1) (a) and (d) only
(2) (b), (c), (d) and (e) only
(3) (a), (b), (d) and (e) only
(4) (b) and (c) only
Answer: (4) Axolemma is more permeable to negatively charged proteins present in the axoplasm.
(1) Corpus albicans
(2) Corpus callosum
(3) Corpus striatum
(4) Corpus spongiosum
Answer: (2) Corpus callosum
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(Session 2026 - 27)