Chapter 5: Nervous System

Select the correct answer:

1. Reaction to any stimulus is called:

A) receptor

B) impulse

C) responses

D) effector

Answer: C) responses

Explanation: A response is the reaction of an organism to a stimulus. The sequence is: Stimulus [source symbol unavailable] Receptor [source symbol unavailable] Coordinator (CNS) [source symbol unavailable] Effector [source symbol unavailable] Response. An impulse is the electrical signal traveling along a neuron. An effector is the muscle or gland that carries out the response.

2. The unit of structure and function in the nervous system is:

A) neuron

B) muscle cell

C) nephron

D) cardiac cell

Answer: A) neuron

Explanation: The neuron (nerve cell) is the structural and functional unit of the nervous system. It is specialized for transmitting electrical impulses. A nephron is the functional unit of the kidney, and muscle cells are part of the muscular system.

3. Thyroid gland has the ability to store:

A) Iodine

B) chlorine

C) fluorine

D) zinc

Answer: A) Iodine

Explanation: The thyroid gland actively absorbs and stores iodine from the blood. Iodine is essential for the synthesis of thyroid hormones, thyroxine (T4) and triiodothyronine (T3), which regulate metabolism.

4. Endocrine glands pour their secretion directly into:

A) lymph

B) blood

C) organs

D) muscles

Answer: B) blood

Explanation: Endocrine glands are ductless glands that secrete hormones directly into the bloodstream. The blood then transports these hormones to target cells and organs throughout the body. Exocrine glands secrete through ducts to the surface or into cavities.

5. Islet of Langerhans are parts of the:

A) thyroid gland

B) adrenal gland

C) pancreas

D) gonads

Answer: C) pancreas

Explanation: The Islets of Langerhans are clusters of cells within the pancreas that function as an endocrine gland. They contain alpha cells (secrete glucagon), beta cells (secrete insulin), and delta cells (secrete somatostatin).

6. Nerve impulse is best described as:

A) chemical

B) electrical

C) osmotic

D) electrochemical

Answer: D) electrochemical

Explanation: A nerve impulse is best described as an electrochemical signal. It involves the movement of ions (electrical) across the neuron membrane and the release of neurotransmitters (chemical) at synapses to transmit the signal to the next neuron.

7. When a person is frightened, which substance increases the blood sugar level?

A) adrenaline

B) amylase

C) glycogen

D) insulin

Answer: A) adrenaline

Explanation: Adrenaline (epinephrine) is the "fight or flight" hormone released by the adrenal medulla during stress or fear. It stimulates the breakdown of glycogen into glucose in the liver, increasing blood sugar levels to provide quick energy.

8. Which part of the brain detects temperature changes in the blood?

A) cerebellum

B) cerebral hemispheres

C) hypothalamus

D) medulla

Answer: C) hypothalamus

Explanation: The hypothalamus contains thermoreceptors that monitor the temperature of the blood. It acts as the body's thermostat, initiating responses like sweating or shivering to maintain a stable core temperature.

10. In contrast to nerve, the response produced by hormones takes longer because:

A) hormones are specific in their action.

B) hormones are transported through blood.

C) hormones are produced in small amounts.

D) the molecules of hormones are small in size.

Answer: B) hormones are transported through blood.

Explanation: Hormones are secreted into the bloodstream and must travel to target cells, which takes time. In contrast, nerve impulses travel rapidly along dedicated neurons, allowing for immediate responses.

11. Once released, neurotransmitter molecules typically produce signals in postsynaptic neurons by:

A) entering the postsynaptic neuron

B) attaching to vesicles

C) binding to presynaptic receptors

D) binding to postsynaptic receptors

Answer: D) binding to postsynaptic receptors

Explanation: Neurotransmitters diffuse across the synaptic cleft and bind to specific receptor proteins on the postsynaptic membrane. This binding triggers an electrical change in the postsynaptic neuron, propagating the signal.

12. The parts of brain represented by I and II are: (Diagram of brain with labels I and II)

Answer: A) cerebellum, pons (Note: Based on the diagram, I points to the cerebellum, and II points to the pons.)

13. The diagram shows Reflex arc. The components of this reflex arc are:

Answer: D) Receptor, Sensory neuron, Interneuron, Motor neuron, Effector

Explanation: The correct sequence of a reflex arc is: Receptor [source symbol unavailable] Sensory (Afferent) Neuron [source symbol unavailable] Interneuron (in CNS) [source symbol unavailable] Motor (Efferent) Neuron [source symbol unavailable] Effector.

14. Four characters of a specific hormone are listed below:

1. What is nervous system?

Answer: The nervous system is a complex network of specialized cells (neurons) that coordinates the actions and sensory information of an organism by transmitting signals to and from different parts of the body. It consists of the central nervous system (brain and spinal cord) and the peripheral nervous system (nerves).

2. What is the role of nervous system?

Answer: The nervous system has three main roles:

1. Sensory Input: Detecting stimuli from the internal and external environment.

2. Integration: Processing and interpreting sensory information.

3. Motor Output: Initiating responses by activating muscles or glands (effectors).

3. Differentiate between central nervous system and peripheral nervous system.

Answer:

Divisions None. Somatic and Autonomic.

4. Name the parts of human brain.

Answer: The main parts of the human brain are:

1. Cerebrum: Largest part; controls intelligence, memory, and voluntary actions.

2. Cerebellum: Coordinates balance, posture, and smooth muscle movements.

3. Brainstem: Includes midbrain, pons, and medulla oblongata; controls involuntary functions.

4. Diencephalon: Includes thalamus and hypothalamus; relays sensory information and regulates homeostasis.

5. Write two functions of cerebellum.

Answer: Two functions of the cerebellum:

1. Coordination: It coordinates voluntary movements like walking, talking, and writing.

2. Balance: It maintains posture and balance by processing input from the inner ear and muscles.

6. How are brain and spinal cord protected?

Answer: The brain and spinal cord are protected by:

1. Bone: The brain is enclosed in the skull (cranium), and the spinal cord is protected by the vertebral column.

2. Meninges: Three protective membranes (dura mater, arachnoid mater, pia mater) surround the CNS.

3. Cerebrospinal Fluid (CSF): A fluid that cushions the brain and spinal cord, providing shock absorption.

7. What are the types of neuron? What are their functions?

Answer: Types of neurons:

1. Sensory (Afferent) Neurons: Carry impulses from sensory receptors to the CNS.

2. Motor (Efferent) Neurons: Carry impulses from the CNS to effectors (muscles/glands).

3. Interneurons: Connect sensory and motor neurons within the CNS; process information.

8. Define stimulus with examples.

Answer: A stimulus is any detectable change in the internal or external environment that provokes a response in an organism. Examples include light, sound, temperature, pressure, and chemicals. Example: Touching a hot object (stimulus) causes withdrawal of the hand (response).

9. Define and sketch synapse.

Answer: A synapse is the junction between two neurons or between a neuron and an effector cell, where a nerve impulse is transmitted. (Diagram Description) The synapse consists of a presynaptic knob (axon terminal), a synaptic cleft (gap), and a postsynaptic membrane (dendrite or cell body of the next neuron). Neurotransmitters are released from vesicles in the presynaptic knob into the cleft.

10. How does an impulse cross a synapse?

Answer: When an impulse reaches the presynaptic knob, it causes calcium channels to open. Calcium influx causes synaptic vesicles

to fuse with the membrane and release neurotransmitters into the synaptic cleft. The neurotransmitters diffuse across the cleft and bind to receptors on the postsynaptic membrane, triggering a new electrical impulse.

11. What action or change do neurotransmitters transmit to the target cell?

Answer: Neurotransmitters transmit either an excitatory or inhibitory signal to the target cell. Excitatory neurotransmitters (e.g., glutamate) depolarize the postsynaptic membrane, making an action potential more likely. Inhibitory neurotransmitters (e.g., GABA) hyperpolarize the membrane, making an action potential less likely.

12. What happens to neurotransmitters after they deliver their message?

Answer: After delivering their message, neurotransmitters are removed from the synaptic cleft by:

1. Reuptake: Reabsorbed by the presynaptic neuron.

2. Enzymatic Degradation: Broken down by enzymes (e.g., acetylcholinesterase).

3. Diffusion: Diffusing away from the cleft.

13. How many different types of neurotransmitters are there?

Answer: There are over 100 known neurotransmitters. Major types include:

Acetylcholine Biogenic Amines: Dopamine, serotonin, norepinephrine. Amino Acids: GABA, glutamate, glycine. Peptides: Endorphins, enkephalins. Gases: Nitric oxide.

14. What is a reflex action?

Answer: A reflex action is a rapid, involuntary, and automatic response to a stimulus. It occurs without conscious thought, protecting the body from harm. Examples include the knee-jerk reflex and withdrawing the hand from a hot object.

15. Name the endocrine glands of man.

Answer: Endocrine glands in man include:

1. Hypothalamus

2. Pituitary gland

3. Pineal gland

4. Thyroid gland

5. Parathyroid glands

6. Thymus

7. Adrenal glands

8. Pancreas (Islets of Langerhans)

9. Gonads (Ovaries and Testes)

16. Name the hormones secreted by each of the endocrine gland.

Answer:

Hypothalamus: Releasing and inhibiting hormones. Pituitary: GH, TSH, ACTH, FSH, LH, Prolactin, ADH, Oxytocin. Thyroid: Thyroxine (T4), Triiodothyronine (T3), Calcitonin. Parathyroid: Parathyroid Hormone (PTH).

Adrenal Cortex: Cortisol, Aldosterone, Androgens. Adrenal Medulla: Adrenaline, Noradrenaline. Pancreas: Insulin, Glucagon, Somatostatin. Ovaries: Estrogen, Progesterone. Testes: Testosterone.

17. Differentiate between: cerebrum and cerebellum, sensory and motor neuron, voluntary and involuntary action, nerve impulse and hormonal transmission, endocrine glands and exocrine glands.

Answer:

Cerebrum vs. Cerebellum: Cerebrum controls intelligence and voluntary actions; Cerebellum controls balance and coordination. Sensory vs. Motor Neuron: Sensory neurons carry impulses to CNS; Motor neurons carry impulses away from CNS. Voluntary vs. Involuntary Action: Voluntary actions are under conscious control; Involuntary actions are automatic. Nerve Impulse vs. Hormonal Transmission: Nerve impulse is electrical and fast; Hormonal transmission is chemical and slower. Endocrine vs. Exocrine Glands: Endocrine glands are ductless and secrete hormones into blood; Exocrine glands have ducts and secrete onto surfaces.

1. Describe the nervous system and its role in man.

Answer: The human nervous system is a complex network that coordinates all body activities.

Divisions:

1. Central Nervous System (CNS): Brain and spinal cord. It is the integration and command center.

2. Peripheral Nervous System (PNS): All nerves outside the CNS. It connects the CNS to the rest of the body.

Role:

Sensory Input: Detects changes in the environment. Integration: Processes and interprets sensory information. Motor Output: Initiates appropriate responses. Homeostasis: Regulates internal conditions. Higher Functions: Enables thought, memory, and emotions.

In summary, the nervous system is essential for survival, enabling rapid responses and coordination.

2. Draw a vertical section of human brain and label it. Write the functions of each part.

Answer: (Diagram Description)

Cerebrum: Largest part, divided into hemispheres. Controls intelligence, memory, and voluntary actions. Cerebellum: Located below the cerebrum. Coordinates balance, posture, and smooth movements. Medulla Oblongata: Controls involuntary functions like heart rate, breathing, and blood pressure. Pons: Relays signals between cerebrum and cerebellum. Hypothalamus: Regulates body temperature, hunger, thirst, and hormone secretion. Thalamus: Relay center for sensory information.

In summary, each part of the brain has specific functions essential for life.

3. Draw labeled cross section of human spinal cord and write its structure and function.

Answer: (Diagram Description)

Gray Matter: Inner butterfly-shaped region containing cell bodies. White Matter: Outer region containing myelinated axons. Central Canal: Contains cerebrospinal fluid.

Structure: The spinal cord is a long, cylindrical structure extending from the medulla oblongata. It has 31 pairs of spinal nerves.

Function:

Conduction: Carries sensory information to the brain and motor commands from the brain. Reflex Center: Mediates reflexes.

In summary, the spinal cord is vital for communication and reflexes.

4. Outline the types of neuron with diagram.

Answer: (Diagram Description)

1. Sensory Neuron: Has a cell body in the dorsal root ganglion. Transmits impulses from receptors to CNS.

2. Motor Neuron: Has a cell body in the ventral horn. Transmits impulses from CNS to effectors.

3. Interneuron: Located entirely within the CNS. Connects sensory and motor neurons.

In summary, each type of neuron has a specific role in the nervous system.

5. Explain that nerve impulses are electrical that travel across neuron.

Answer: A nerve impulse is an electrochemical signal. It begins when a stimulus causes sodium channels to open, allowing Na⁺ to rush into the neuron. This depolarizes the membrane, creating an action potential. The action potential travels along the axon as adjacent sodium channels open. After the impulse passes, potassium channels open, repolarizing the membrane. This electrical wave travels rapidly along the neuron.

6. What are neurotransmitters?

Answer: Neurotransmitters are chemical messengers that transmit signals across a synapse from one neuron to another or to an effector cell. They are stored in synaptic vesicles, released into the synaptic cleft, and bind to receptors on the postsynaptic membrane. Examples include acetylcholine, dopamine, and serotonin.

7. Explain reflex action with diagram.

Answer: (Diagram Description)

Receptor: Detects stimulus. Sensory Neuron: Transmits impulse to spinal cord. Interneuron: Processes information. Motor Neuron: Transmits impulse to effector. Effector: Muscle or gland that responds.

Explanation: A reflex action is a rapid, involuntary response. Example: Touching a hot object [source symbol unavailable] receptor in skin [source symbol unavailable] sensory neuron [source symbol unavailable]

spinal cord [source symbol unavailable] motor neuron [source symbol unavailable] muscle contracts [source symbol unavailable] hand withdraws.

In summary, reflex actions protect the body from harm.

8. Identify the major endocrine hormones with their functions.

Answer:

Testes Testosterone Male secondary sex characteristics.

In summary, hormones regulate almost all body functions.