Central Nervous System Functions and Anatomy

• Biology 8 focuses on Science and Health, with the theme: Live 5C's (Competence, Character, Commitment to Achieve, Collaboration, Creativity) through Academic Rigor, Growth Mindset and Grit.
• Unit 02 covers life processes of living things, specifically focusing on the nervous system as a human system.

Nervous System Introduction

• Nervous System's main functions: receives, interprets, and responds to information from the environment and inside the body.

Central Nervous System (CNS)

• CNS consists of the brain and the spinal cord. It processes and sorts information to determine appropriate actions.

Brain

• The brain is one of the largest organs and coordinates most body activities.
• It is the center for thought, memory, judgment, and emotion, responsible for various body function controls like temperature and breathing.

Brain Sections

• The brain has three sections: forebrain, midbrain, and hindbrain.

Forebrain

• Forebrain components: cerebrum, cortex, thalamus, hypothalamus.

Cerebrum

• The cerebrum is the largest brain section, located in the upper portion.
• The cerebrum processes thoughts, judgement, memory, problem-solving, and language.
• The outer layer is the cerebral cortex composed of grey matter.
• The cerebrum is divided into cerebral hemispheres, each with four lobes.
• The left hemisphere is logical and analytical, while the right is intuitive and creative.

Lobes of Cerebrum

• Frontal lobe: anterior portion controlling motor function, personality and speech.
• Parietal Lobe: superior portion interpreting sensory nerve impulses and language.
• Occipital lobe: posterior portion, controls vision.
• Temporal lobe: lateral portions, controlling hearing and smell.

Cortex

• The Cortex is the outer layer of the cerebrum, also known as the "gray matter".
• Information from the five senses enters the brain via the spinal cord to the cortex.
• Cortex information is then directed throughout the nervous system for further processing.

Thalamus

• Thalamus carries messages to the cortex from sensory organs such as eyes, ears, nose, and fingers.

Hypothalamus

• Hypothalamus controls automatic body processes like pulse, thirst, appetite, and sleep patterns.
• It controls the pituitary gland which produces hormones that control metabolism, digestion, growth, sexual maturity, and stress response.

Midbrain

• Midbrain: Located under the forebrain midpoint.
• It acts as a coordinator for messages entering and exiting the brain to the spinal cord.

Hindbrain

• Hindbrain: Located underneath the cerebrum's back end.
• Hindbrain components: cerebellum, pons, and medulla oblongata.

Cerebellum

• Cerebellum: Second largest part of the brain that coordinates voluntary body movements, maintains balance, and refines muscular movements initiated in the cerebrum.

Brainstem

• Pons: Largest part of the brainstem connecting cerebrum and cerebellum.
• Medulla Oblongata: Plays a key role transmitting signals and controlling autonomic activities such as heartbeat and respiration.
• The Brainstem: Sends out and coordinates all of the brain's messages and controls autonomic functions like breathing, heart rate, blood pressure, swallowing, digestion, and blinking.

Spinal Cord

• The spinal cord connects the peripheral nervous system and brain, serving as an information pathway.
• It also handles some sensory information and motor responses independently from the brain. Called a reflex action.
• Spinal cord regions: cervical (7), thoracic (12), lumbar (5), sacral (5), and coccygeal (4).
• The spinal cord gives rise to 31 spinal nerve pairs in 33 pieces of the spinal column.

Meninges

• Meninges: Membranous coverings of the brain and spinal cord.
• Three layers: dura mater, arachnoid mater, and pia mater. They provide a supportive framework for cerebral and cranial vasculature.
• Dura mater: outermost layer continuous with epineurium of the spinal nerves.
• Arachnoid mater: thin and wispy.
• Pia mater: tightly bound to the surface.

Sulci & Gyri

• Sulci: Grooves that create wrinkles in the brain.
• Gyri: Ridges between the grooves.
• Gyri singular (Gyrus): Elevated tissue ridges surrounding the cerebral hemisphere.
• Sulci singular (Sulcus): Depression, or groove in the cerebral cortex.

Fissure

• Fissure: Also called a sulcus.
• A Fissure is a groove, natural division, or cleft in the body.
• Sulci are shallower grooves surrounding a gyrus.
• Fissures are larger furrows that divide the brain into lobes and hemispheres like the medial longitudinal fissure.

Cerebrospinal Fluid (CSF)

• CSF is a clear, colorless liquid filling and surrounding the brain and spinal cord, providing a mechanical barrier against shock.
• It is primarily formed in the choroid plexus of the ventricles of the brain.
• Choroid Plexus: A network of blood vessels in each ventricle and is derived from the pia mater.
• Greek origin: "khorion" means “membrane enclosing the fetus"; plexus means network.

Peripheral Nervous System (PNS)

• The PNS contains all nerves outside the central nervous system (CNS).
• Its serves to connect the CNS to organs, limbs, and skin extending to periphery of the body.

PNS Schemes

• Sensory or afferent division.
• Motor or efferent division.

Sensory/Afferent Division

• Sensory/Afferent Division: Consists of nerve fibres that convey the impulses to the central nervous system from the sensory receptors in the body.

Motor/Efferent Division

• Motor/Efferent Division carries impulses from the CNS to effector organs creating a motor response.
• The PNS consists of two nervous systems; the Somatic and the Autonomic Nervous Systems

Somatic Nervous System

• Somatic: Carries sensory and Motor information to and from the central nervous system.
• Derives its name from the greek word "soma" meaning "body".
• Contains sensory and motor nuerons for voluntary movement:
  • Afferent (sensory) neurons carry information from the nerves to the central nervous system
  • Efferent (motor) neurons transmit information from the brain and spinal cord to muscle fibers throughout the body.

Autonomic Nervous System

• The autonomic nervous system regulates involuntary body functions like blood flow, heartbeat, digestion, and breathing.
• The autonomic nervous system is divided into two branches; the Sympathetic and Parasympathetic Systems
  • The Sympathetic activates "fight or flight"
  • The Parasympathetic maintains normal body functions and homeostasis

Sympathetic System:

• Located to the sympathetic chain that connects to skin, blood vessels, and organs, with ganglias on both sides of the spine.
• The sympathetic system:
  • stimulates heartbeat
  • raises blood pressure
  • dilates the pupils and the trachea and bronchi
  • stimulates glycogenolysis converting liver glycogen to glucose
  • shunts blood away from the skin and viscera to the skeletal muscles, brain, and heart
  • inhibits peristalsis in the gastrointestinal (GI) tract.
  • inhibits contraction of the bladder and rectum
  • increases AMPA receptors, in rats and mice, in the hippocampus

Parasympathetic System:

• Branch of Autonomic Nervous System (ANS) returns the body to a balanced state ("homeostasis") after experiencing pain or stress.
• Parasympathetic Stimulation:
  • slowing down of the heartbeat
  • lowering of blood pressure
  • constriction of the pupils
  • increased blood flow to the skin and viscera
  • peristalsis of the Gl tract

Spinal Nerve

• Spinal Nerves: Nerve roots branch off spinal cord and pass through vertebrae holes called the Foramen.
• Spinal Nerves carry information from the spinal cord to the rest of the body, and from the body back up to the brain.

Cranial Nerves

• Nerves: Emerge directly from the brain.
• There are traditionally twelve pairs of cranial nerves that are classified as Sensory, Motor or Mixed:
  • Sensory; CN I, CN II, CN VIII
  • Motor; CN III, CN IV, CN VI, CN XI, CN XII
  • Mixed; CN V, CN VII, CN IX and CN X

Nerve cells or Neurons:

• Neurons: The active parts of the nervous system.
• Neurons communicate with each other and other cells through electrical impulses enabling effector organs to respond to stimuli.
• A Neuron consists of an; Axon, Dendrites and Synapses

Neuron - Axon;

• Axon: A slender projection of a nerve that conducts electrical impulses away from the neuron's cell body or soma.
• Axons take information away from the cell body with a myelin sheath.

Neuron - Dendrites;

• Dendrite: treelike branches serving as the main part of the neuron.
• They receive the signals from other nerve cells bringing information to the cell body and lack myelin sheath:

Neuron - Synapses;

• Synapse: Site of transmission of electrical nerve impulses between nerve cells, and between a neuron and a muscle.
• A synaptic connection between a neuron and a muscle cell is called a neuromuscular junction
• The next topic will be the skeletal system

Test your knowledge of the central nervous system (CNS) and its functions. This quiz covers the primary functions of the CNS, the roles of different brain regions, and the impact of damage to specific areas. Questions cover topics ranging from the cerebral hemispheres to the medulla oblongata.