Central Nervous System Overview

Central Nervous System (CNS)

• CNS comprises the brain and spinal cord, containing all neuron components.
• The brain houses centers directing nervous system regions.
• Sheep brains are commonly used for study due to their accessibility and large discernible parts.
• Ventricles are interconnected spaces containing cerebrospinal fluid (CSF), cushioning the brain.

Brain Structures

• Cerebrum: Largest, most developed brain region; responsible for higher functions.

  • Divided into left and right hemispheres connected by the corpus callosum, a sheet of white matter.
  • Divided into lobes:
    • Frontal Lobe: Controls motor functions, voluntary movement, cognition, problem-solving, speech, and smell.
    • Parietal Lobe: Receives sensory input from skin and taste receptors (gustatory cortex). Separated from the frontal lobe by the central sulcus.
    • Occipital Lobe: Processes visual input, integrating with other sensory data. Optic nerves split at the optic chiasma (in the diencephalon) to reach opposite brain sides.
    • Temporal Lobe: Houses sensory areas for hearing and smell, including the olfactory bulb (olfactory cortex). Olfactory bulb receives nerve impulses from olfactory cells in the nose.

• Diencephalon: Region housing the third ventricle and crucial structures:

  • Thalamus: Two connected lobes, highest brain area receiving sensory impulses; "gatekeeper," controlling sensory data to the cerebrum.
  • Hypothalamus: Forms third ventricle floor; controls homeostasis (appetite, body temperature, blood pressure, water balance), as well as pressure, reproductive behavior, hostility, and pain.

• Cerebellum: Coordinates balance, equilibrium, and smooth motor activity.

• Brainstem: Connects brain and spinal cord; includes pons and medulla oblongata. Controls vital functions (e.g., internal organ functions, breathing, heart rate, blood pressure) and serves as a relay station for nerve impulses. Subdivisions:

  • Midbrain: Sensory and motor relay station, eye muscle reflex center, hearing, and motor coordination.
  • Pons: Pathway for nerve impulses between medulla and the higher brain.
  • Medulla Oblongata: Controls vital functions such as heart rate, blood pressure, and breathing, and serves as a relay station for nerve impulses between the spinal cord and higher brain centers; also involved in swallowing, digestion, and vomiting.

Human Brain

• Cerebrum: Largest portion; controls thinking, memory, emotion, decision-making, sensation, movement, and coordination of voluntary actions. Divided into two symmetrical hemispheres.

• Cerebellum: Aids in balance, coordination, and fine motor skills.

• Diencephalon: Includes:

  • Thalamus: Relays sensory information, processes sensory signals (touch, sight, sound, taste) and sends it to the cerebrum for processing; crucial in alertness and sleep regulation.
  • Hypothalamus: Maintains homeostasis (hunger, thirst, body temperature, circadian rhythms); controls endocrine system and affects stress and growth.

• Brainstem: Includes:

  • Midbrain: Communication center and controls eye movement, processing hearing and motor control.
  • Pons: Regulates breathing and supports smooth coordination and balance.
  • Medulla: Controls vital functions (heart rate, blood pressure, breathing), swallowing, and digestion.

Vertebrate Brain Comparison

• Vertebrate brains feature a forebrain, midbrain, and hindbrain.
• Early vertebrates showed specialization: forebrain (smell), midbrain (sight), hindbrain (hearing/balance).
• Forebrain: Contains olfactory bulb and cerebrum.
• Midbrain: Contains optic lobe.
• Hindbrain: Contains cerebellum.
• In fishes and amphibians, the midbrain is a dominant center for control, while fish, bird, and mammal cerebrums are well-developed and increase in complexity.

Spinal Cord

• Located in the mid-dorsal region, protected by the vertebral column.
• Grey Matter: Butterfly-shaped core of short nerve fibers, interneurons, and motor neuron cell bodies.
• White Matter: Contains long nerve fibers (with insulating myelin sheaths) carrying impulses up and down the cord.

Peripheral Nervous System (PNS)

• Includes 12 pairs of cranial nerves and 31 pairs of spinal nerves.
• Cranial nerves facilitate communication between the head, neck, and face and the brain.

Spinal Nerves

• Each nerve contains sensory and motor neuron fibers.
• Sensory Neuron: Carries impulses from sensory receptors to spinal cord; cell body in dorsal root ganglion.
• Interneuron: Located in the spinal cord; relays information between sensory and motor neurons, some also relaying information to and from the brain.
• Motor Neuron: Carries impulses from the spinal cord to effectors (muscles), causing contraction in response to stimuli.

Spinal Reflexes

• Reflexes are involuntary, predictable responses to stimuli, enabling rapid reactions.
• Sequence of a spinal reflex: Receptor detects stimulus → sensory neurons conduct impulse to spinal cord interneurons → interneurons relay impulse via motor neurons to effectors (muscles.)
• Example (knee-jerk reflex): Tapping patellar tendon stretches muscle, stimulating receptor → sensory input, spinal cord, motor output → muscle contraction.

Experimental Procedure (Knee-Jerk Reflex)

• Tapping the patellar tendon stretches the attached muscle, generating nerve impulses → sensory neurons → spinal cord → motor neurons → muscle contraction. These reflexes help maintain balance and posture.

Explore the components and functions of the Central Nervous System (CNS), focusing on the brain and spinal cord. Discover the significance of different brain structures and their roles in higher functions, as well as the importance of sheep brains in studies. This quiz delves into the intricacies of cerebrum, lobes, and overall CNS functionality.