If I Only Had a Brain

If I only had a brain………

Meninges –membranes between bone and tissue protecting brain and spinal cord

3 layers of meninges:

Dura mater-white fibrous CT, blood vessels and nerves, attaches to inside of cranial cavity, forms periosteum

Arachnoid mater-middle, weblike, no blood vessels

Pia mater-innermost, thin, contains nerves and blood vessels, hugs organs Cerebrospinal fluid-between arachnoid and pia mater, fill ventricles

Brain—3 lb mass 100 billion multipolar neurons

3 portions 1. Cerebrum-largest, nerve centers for sensory and motor, higher mental functions  Halves are cerebral hemispheres, connected by nerve fibers—corpus callosum, separated by longitudinal fissure  Ridges are convolutions (gyri)  Shallow grooves=sulci  Deep grooves=fissures  Lobes: Frontal (motor areas), parietal, temporal, occipital, insula  Outermost portion-cerebral cortex  Nerve fibers cross over—motor area on right controls left skeletal muscles  Hemisphere dominance—one side of cerebrum controls certain functions—Left hemi dom. In 90% of people.

2. Cerebellum-centers for voluntary muscle mvmt.  Posture, position of body parts 3. Brain stem-connect parts of nervous system and regulate visceral (organ) activities  Midbrain-reflex centers  Pons-relays impulses  Medulla Oblongata-cardiac, vasomotor, and respiratory centers

4. Diencephalon-contains Thalamus-sensation awareness Pituitary gland-growth hormones and reproductive hormones Hypothalamus-regulates visceral activity, overall homeostasis Limbic system-controls emotions

Spinal cord -Nerve column from foramen magnum to intervertebral disk between L1 and L2 vertebrae

-31 segments (spinal nerves)

White matter-myelinated fibers Gray matter-unmyelinated nerve fibers and neuron cell bodies Function of spinal cord: 1. Conducts nerve impulses 2. Center for spinal reflexes Ascending tracts carry info to brain Descending tracts carry info from brain

Peripheral Nervous system –nerves that branch off CNS, divided into Somatic and Autonomic Somatic N.S.-Connects CNS to skin and skeletal muscles for conscious activity

Autonomic Nervous system- Controls automatic processes, connects to viscera (organs) Regulates processes to keep body functioning 2 divisions Sympathetic division-prepares body for stress (fight or flight) Parasympathetic-active under ordinary, restful conditions, restores rest after stress