12.3.1 Identify Parts of the Brain
- Forebrain: Includes cerebrum, thalamus, hypothalamus, pituitary gland.
- Midbrain: Relay center for visual and auditory impulses.
- Hindbrain: Includes cerebellum, pons, medulla oblongata.
12.3.2 Explain Function of the Parts of Brain
- Cerebrum: Controls voluntary actions (e.g., movement, speech), memory, reasoning, sensory processing.
- Cerebellum: Coordinates balance, posture, and fine motor skills (e.g., walking, writing).
- Pituitary Gland: Secretes hormones regulating growth, metabolism, and other endocrine glands.
- Hypothalamus: Regulates homeostasis (e.g., temperature, hunger, thirst) and controls pituitary hormone release.
- Medulla Oblongata: Controls involuntary actions (e.g., heart rate, breathing, swallowing).
12.3.3 Differentiate Between Cross-Sectional Views of Brain and Spinal Cord (White and Grey Matter)
Brain:
- Grey Matter: Outer layer (cortex) in cerebrum and cerebellum; contains neuron cell bodies for processing information.
- White Matter: Inner region; contains myelinated axons for signal transmission between brain regions.
Spinal Cord:
- Grey Matter: Central, butterfly-shaped region; contains neuron cell bodies for reflex and signal processing.
- White Matter: Surrounds grey matter; contains myelinated axons for signal transmission to/from the brain.
12.3.4 Define Neuron
A neuron is a specialized cell that transmits electrical and chemical signals in the nervous system. It consists of a cell body, dendrites (receive signals), and an axon (transmits signals).
12.3.5 Differentiate Among Sensory, Motor, and Relay Neurons
| Neuron Type | Structure | Function | Example |
| Sensory | Long dendrite, short axon; connects receptors to CNS. | Transmits signals from receptors to CNS. | Neurons in skin detecting touch. |
| Motor | Short dendrites, long axon; connects CNS to effectors. | Transmits signals from CNS to muscles/glands. | Neurons triggering muscle contraction. |
| Relay | Short dendrites and axons; found in CNS. | Connects sensory and motor neurons; processes signals. | Interneurons in spinal cord for reflexes. |
12.3.6 Differentiate Between Voluntary and Involuntary Actions
Voluntary Actions:
- Controlled consciously by the cerebrum.
- Examples: Writing, speaking, kicking a ball.
Involuntary Actions:
- Controlled unconsciously by the medulla, cerebellum, or spinal cord.
- Examples: Heartbeat, blinking, reflex withdrawal from pain.
12.3.7 Reflex Action and Reflex Arc
Reflex Action: Rapid, involuntary response to a stimulus to protect the body (e.g., pulling hand from a hot surface).
Reflex Arc: Neural pathway for a reflex action, involving:
Receptor → Sensory neuron → Relay neuron (in spinal cord) → Motor neuron → Effector.
12.3.8 Trace the Path of a Nervous Impulse in a Reflex Action
Example: Touching a hot surface:
- Receptor in skin detects heat.
- Sensory neuron transmits impulse to spinal cord.
- Relay neuron in spinal cord processes the signal and synapses with a motor neuron.
- Motor neuron carries impulse to effector (arm muscle).
- Effector contracts, pulling the hand away.