The Nervous SystemPart III

The central nervous system

• The central nervous system consists of the brain and spinal cord.

The spinal cord

• The spinal cord carries sensory information from receptors all over the body to the brain, and relays motor information from the brain to muscles, organs, and glands.

The brain

• Enclosed within the skull, the brain is surrounded by a tough three-layer protective membrane called the meninges.

• The meninges form the blood-brain barrier, which determines what substances will reach the brain through the circulatory system.

• Cerebrospinal fluid circulates between the innermost and middle meninges of the brain and through the central canal of the spinal cord.

Spinal tap

The brain

• Brain complexity is one characteristic that distinguishes humans from other animals.

The forebrain

• The forebrain contains paired olfactory lobes, which receive information about smell.

• The cerebrum consists of two very large hemispheres that act as a major coordinating centre from which sensory information and accompanying motor actions originate.

• The cerebral hemispheres are the “location” of speech, reasoning, memory, and personality.

• The surface of the cerebrum is called the cerebral cortex.• The cortex has many folds that increase surface area.

The corpus callosum

• Information stored on one side of the brain is not necessarily present on the the other side.

• The corpus callosum is a large bundle of nerves that allow communication between the two cerebral hemispheres.

The lobes of the cerebrum

The lobes of the cerebrum (forebrain)

Lobe FunctionFrontal lobe • Motor areas control movement of voluntary muscles

(e.g., walking and speech).• Association areas are linked to intellectual activities and

personality.

Temporal lobe • Sensory areas are responsible for vision and hearing.• Association areas are linked to memory and

interpretation of sensory information.

Parietal lobe • Sensory areas are responsible for touch and temperature awareness.

• Association areas are linked to emotions and interpreting speech.

Occipital lobe • Sensory areas are responsible for vision.• Association areas interpret visual information.

The primary motor cortex and primary somatosensory cortex

Other parts of the forebrain

• Below the cerebrum is the thalamus, and immediately below the thalamus is the (you guessed it!) hypothalamus. A direct connection between the hypothalamus and the pituitary gland unites the nervous system with the endocrine system.

The midbrain and hindbrain

• The midbrain is less developed than the forebrain.• The midbrain acts as a relay centre for eye and ear

reflexes.• The hindbrain is found posterior to the midbrain and joins

with the spinal cord.• The cerebellum, located underneath the cerebral

hemispheres, is the largest section of the hindbrain.• The cerebellum coordinates all muscle actions, and

controls and synchronizes limb movements, balance, and muscle tone.

The midbrain and hindbrain

• The pons (meaning “bridge”) is largely a relay station that passes information between regions of the cerebellum and between the cerebellum and the medulla.

• The posterior region of the hindbrain is the medulla oblongata. Nerve tracts from the spinal cord and higher brain centres run through the medulla, which acts as a connection between the PNS and CNS.

• The medulla controls involuntary muscle action (including breathing movements, muscles controlling blood vessel diameter, and the maintenance of heart rate).

Anatomy of the human brain

Anything after here is just fun stuff to know (i.e. it won’t be

on the quiz)

*WARNING: Graphic images ahead. Viewer discretion is

strongly advised…

Human brain mapping

“That’s odd, I smell freshly baked peanut butter cookies….”

Human brain mapping

Phineas Gage - unintentional self-inflicted frontal lobotomy, involving a tamping rod and some dynamite…

Human brain mapping

Magnetic Resonance Image (MRI) of a normal human brain

The autonomic nervous system and homeostasis

• The autonomic system is made up of two distinct (and often opposing) units: the sympathetic nervous system and the parasympathetic nervous system.

Organ Sympathetic ParasympatheticHeart ↑ heart rate ↓ heart rateDigestive system ↓ peristalsis ↑ peristalsisLiver ↑ release of glucose Storage of glucoseEyes Dilates pupils Constricts pupilsBladder Relaxes sphincter Contracts sphincterSkin ↑ blood flow ↓ blood flowAdrenal gland Causes release of

epinephrineNo effect

Drugs and the brain

• Many types of drugs (pharmaceutical or otherwise) mimic naturally occuring neurotransmitters – these include pain-killers, stimulants, depressants, and anaesthetics (both general and local).

THE END