Human Nervous System and Reflex Actions Review

Flashcards covering the Central Nervous System, Peripheral Nervous System, brain regions, types of neurons, voluntary/involuntary actions, and reflex arcs based on the provided textbook notes.

What two main components comprise the Central Nervous System (CNS)?

The Central Nervous System comprises the brain and the spinal cord.

What is the bony skull that encloses the human brain called?

Cranium.

What are the weight and approximate number of neurons in an adult human brain?

An adult brain weighs about $1.5\,\text{kg}$ and consists of about one hundred billion ($100\text{ billion}$) neurons.

Which major parts of the human brain are shown in this structural diagram?

Figure 2.4 shows the forebrain (cerebrum, thalamus, hypothalamus), midbrain, and hindbrain (cerebellum, pons, medulla oblongata).

What are the three main parts of the forebrain?

Cerebrum, thalamus, and hypothalamus.

What functions are controlled by the left and right cerebral hemispheres?

The left hemisphere controls speech, comprehension, arithmetic, and writing. The right hemisphere controls spatial ability, artistic, and musical skills.

What are the functions of the thalamus and hypothalamus?

The thalamus controls many sensory functions. The hypothalamus controls body temperature, hunger, and thirst.

What is the primary function of the midbrain?

It receives information from sense organs which is then passed to the appropriate part of the forebrain.

What three structures make up the hindbrain?

Cerebellum, pons, and medulla oblongata.

What is the main function of the cerebellum?

It acts as a controller for maintaining body balance and making precise and accurate movements.

What functions are controlled by the pons?

The pons controls many functions including sleep, swallowing, equilibrium, and taste.

Which part of the hindbrain controls heartbeat, breathing, and digestion, and keeps working when the rest of the brain goes to sleep?

Medulla oblongata.

How is the spinal cord structured and what are its main functions?

The spinal cord is an extension of the medulla oblongata running backwards inside the backbone up to its lower end. Made up of inter-neurons, it links the brain to different body parts and controls some reflex and involuntary actions.

Which structure inside the backbone is shown in this diagram?

Figure 2.5 depicts the spinal cord, which runs backwards inside the backbone and creates a link between the brain and body parts.

What is the Peripheral Nervous System (PNS), and how many cranial and spinal nerve pairs does it contain in humans?

The PNS consists of a network of nerves spreading through the body to connect all parts to the CNS. It contains 12 pairs of cranial nerves and 31 pairs of spinal nerves.

What is a stimulus, and what are receptors?

A stimulus is any internal or external environmental change (such as heat, cold, pressure, or sound) detected by a receptor to initiate a nerve impulse. Receptors are special organs, tissues, or cells that detect stimuli.

What is a nerve?

A cable-like bundle of axons enclosed in a common sheath that transmits messages from one part of the body to another.

How fast can nerve impulses travel?

Nerve impulses may travel as fast as $150\,\text{m/s}$.

What are the three functional types of neurons and their roles?

Sensory neurons carry impulses from sense organs to the CNS. Motor neurons carry impulses from the CNS to effectors (muscles and glands). Inter-neurons are in the CNS and form a link between sensory and motor neurons.

What three functional types of neurons are shown in this figure?

Figure 2.3 shows the structural layout of a sensory neuron, an inter-neuron, and a motor neuron.

What is the functional pathway shown in this diagram of the nervous system?

Figure 2.6 shows how sensory neurons carry impulses from receptors to the central nervous system for processing, and motor neurons carry impulses to effectors (muscles and glands).

What is the key difference between voluntary actions and involuntary actions?

Voluntary actions are performed under conscious control after thinking (e.g., speaking, reading, walking), whereas involuntary actions occur without conscious thinking or control (e.g., heartbeat, breathing, blinking).

What is a reflex action?

An immediate and involuntary response to a stimulus, such as pulling away a hand immediately after touching a hot object.

What is a reflex arc, and what five components complete its pathway?

A reflex arc is the pathway of nerve impulses that completes a reflex action. It consists of a receptor, a sensory neuron, an inter-neuron, a motor neuron, and an effector.

What specific reflex action pathway is demonstrated in this diagram?

Figure 2.7 shows touching a hot object: thermoreceptors in skin receive heat stimulus -> sensory neuron carries impulse to spinal cord inter-neuron -> motor neuron transmits impulse to arm muscles (effectors) -> arm muscles contract to immediately pull the hand back.