The Central Nervous System

Chapter 8.3McGraw-Hill Ryerson

Biology 12 (2011)

All nerves within the PNS contain a thin membrane called the neurilemma

• Neurilemma promotes the regeneration of damaged axons

• Grey Matter– Nerves in the brain and spinal cord (CNS)that lack

myelin and neurilemma• White matter– Nerves in the brain and spinal cord (CNS) that

contain myelin and neurilemma

Central Nervous System (CNS)

• Contains the nerves of the brain and spinal cord– Function = coordinating

center of incoming/outgoing information

Central Nervous System (CNS)

• Brain is found in the skull & serves as overall control center for the nervous system

• Spinal Cord is surrounded by vertebrae and extends down the back of the neck, thorax and abdomen– Center of many reflex actions– Provides a link between sensory and motor nerves

• Both are enclosed in 3 protective membranes called the meninge

• Space between meninge contains cerebrospinal fluid which protects and cushions the CNS

The Brain• 3 big regions made up of little parts– Forebrain• Thalamus: sits at base of forebrain with neurons that connect

to various parts of the brain (“great relay station)• Hypothalamus: controls blood pressure, heart rate, body

temperature, drives (hunger/thirst), and emotions. Abnormalities is linked to violent, unusual behaviour• Cerebrum: largest part of brain (80% of brain weight) and

divided into left and right hemispheres which contain intellect, learning, memory, consciousness, and language

– Midbrain– Hindbrain

The Brain• 3 big regions made up of little parts– Forebrain– Midbrain• Midbrain: found above the pons in brainstem and is involved

in sensory information (eyes, ears, nose) by relaying information between hindbrain and forebrain

– Hindbrain

The Brain• 3 big regions made up of little parts– Forebrain– Midbrain– Hindbrain

• Cerebellum: unconscious coordination of posture, reflexes, body movements, fine/voluntary motor skills, and receives information from specialized sensors (proprioreceptors located within skeletal muscles and joints)

• Medulla oblongata: coordinates reflexes and automatic bodily fnctions that maintain homestasis such as heart rate, constriction or dilation of blood vessels, and rate of breathing, swallowing, and coughing

• Pons: serves as a relay centre between the neurons of the right and left halves of cerebrum, cerebellum, and rest of the brain

The Brain

• Cerebral cortext split into 4 pairs of lobes– Occipital lobe: receives and analyzes visual information

and is needed for recogntion of what is being seen– Temporal lobe: shares in the processing of visual

information but its main function is auditory reception– Parietal lobe: receives and processes sensory information

from the skin, and helps to process information about the body’s position and orientation

– Frontal lobe: integrates information from other parts of the brain and controls reasoning, critical thinking, memory, and personality

The Brain

• Glial cells: non-neural cells that maintain homeostasis, form myelin, deals with waste materials from neurons, and provide support network and protection in the brain.

• Meninges: three layers of tough elastic tissue– Located within skull and spinal column– Directly encloses the brain and spinal cord

Blood-brain barrier

• A protective barrier formed by glial cells and blood vessels that separates the blood from the central nervous system

• selectively controls the entrance of substances into the brain from the blood– Oxygen and glucose are needed by the brain in high and

constant supply and enter the brain through special transport mechanisms

– Caffeine, nicotine, and alcohol are lipid-soluble so they pass directly through the lipid bilayer of the capillaries in the brain

Cerebrospinal Fluid

• Dense, clear liquid from blood plasma found in the ventricles of the brain, in the central canal of the spinal cord, and with the meninges– Transports hormones, white blood cells, and

nutrients across the blood-brain barrier to cells of the brain and spinal cord

– Acts as a shock absorber to cushion the brain

Homework

• Pg 369 #1, 3, 4, 8, 13,