Class 8 General Science Notes: - Unit-2: Human Nervous System: Solved Exercise (Long Questions and Answers)

(National Book Foundation - New Book/New Syllabus Based on National Curriculum Pakistan 2023-2024 and Onwards)

(Class 8 General Science Notes for 8th Centralized Exam 2023-2024 and onward, FDE, Islamabad)

C. Long questions

Q1. Give the structure of the human brain and the roles of different parts of the brain.

Ans:

The brain is protected in the human skull. It is divided into three main parts i.e. forebrain, midbrain, and hindbrain.

Brain

The forebrain further consists of the cerebrum, thalamus, and hypothalamus.

The cerebrum is the largest part of the brain. The human cerebrum is the most advance in all animals. It is divided into the right and left hemispheres. The cerebrum is the site of consciousness (our sense of self memory, intelligence, learning, reasoning, personality, emotions, and will).

Thalamus plays a critical role in the processing of perception. It receives sensory information from the receptor organs and sends them to the specific part of the cerebrum.

Hypothalamus regulates body temperature, appetite, water balance, and blood pressure. It has centres to control mood and emotions, such as aggression, rage, fear, and pleasure.

Midbrain is reduced in humans. It serves as a link between the forebrain and the hindbrain. It also controls the reflex movements of eye muscles.

The hindbrain consists of the cerebellum, pons, and medulla oblongata.

The cerebellum is concerned with the control and precision of all movements involving voluntary muscles.

Pons is a bridge between the cerebellum and other parts of the brain.

Medulla oblongata controls involuntary activities like heart rate, breathing rate, and swallowing. vomiting, salivation, coughing, and sneezing

Q2. Differentiate between the reflex arc and reflex action and explain the pathway followed by nerve impulse in a reflex arc.

Ans:

REFLEX ACTION:

A sudden response to a specific stimulus without conscious control is called a reflex action.

Examples:

The withdrawal of a hand touching a hot object.
Mouthwatering on smelling/ looking/ thinking of delicious food with an empty stomach.
Changing in the shape and size of the inner dark region (pupil) of the eye when seeing in the dark or bright light.

REFLEX ARC:

The reflex arc is a pathway on which nerve impulse travels from the receptor to the effector. The sequence of five pathways of nerve impulse in the reflex arc is as under:

1. Sense organ (receptor)

2. Sensory neuron

3. Interneuron (in CNS)

4. Motor neuron

5. Effector (muscle or gland)

Unit-2: Human Nervous System: Solved Exercise MCQs

Unit-2: Human Nervous System: Solved Long Questions and Answers

Class 8 General Science Notes

Source: General Science Book (National Book Foundation, Pakistan)

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