The Nervous System

Functions of the Nervous System 1. Communication and coordination Adapt and respond to changes from both inside and outside the body 2. Site of reasoning- your brain 3. Two main divisions Central nervous system (CNS): brain and spinal cord Peripheral nervous system- the nerves

Neuron- basic structural unit of the nervous system Dendrites- carry impulses towards the cell Axon-carry impulses away from the cell Myelin sheath Synaptic terminal Epinephrine Norepinephrine Acetylcholine

Nerves are made of many nerve cells Afferent/Sensory-sensory nerves carry message to brain Efferent-motor neurons carry message from brain to muscle Associate- do both and connect the afferent and efferent neurons once they are in the brain Heads up

Central nervous system

Cerebrum-largest part of brain Cerebrum-largest part of brain. Responsible for reasoning, thought, memory, speech, sensation, etc. Divided into two halves/hemispheres Further divided into lobes; occipital, parietal, temporal and frontal

Cerebellum-responsible for muscle coordination Brain stem- most basic functions; respiration, swallowing, blood pressure. Lower part (medulla oblongata) is continuous with spinal cord

General Brain Functions Thalamus Hypothalamus General Brain Functions Brain Waves Sleep Memory/Thought

Memory Memory Short term memory Long term memory persistence of learning over time via the storage and retrieval of information Short term memory activated memory that holds a few items briefly look up a phone number, then quickly dial before the information is forgotten Long term memory the relatively permanent and limitless storehouse of the memory system

Encoding Encoding Effortful Automatic

Encoding Forgetting as encoding failure Which penny is the real thing?

HOMES- Huron, Ontario, Michigan, Erie, Superior Chunking use of acronyms HOMES- Huron, Ontario, Michigan, Erie, Superior ARITHMETIC- A Rat In Tom’s House Might Eat Tom’s Ice Cream organizing items into familiar, manageable units *5 seconds

often occurs automatically like horizontal organization- 177614921812 often occurs automatically

Both the brain and spinal cord are covered by a membrane system called the meninges Spinal cord- begins at foramen magnum and ends at second lumbar vertebrae Contains both afferent (to the brain) and efferent (motor neurons- away from the brain)

Peripheral nervous system Sensory and Motor Divisions Somatic system 12 pairs cranial nerves 31 pairs spinal nerves Autonomic Sympathetic Fight or flight Parasympathetic

Senses Vision -Structures light travels through= Hearing and Balance Outer Middle Inner Smell Taste Touch and Related Senses

The Eye and Vision Vision is the dominant sense in humans 70% of sensory receptors in humans are in the eyes 40% of the cerebral cortex is involved in processing visual information The eye (or eyeball) is the visual organ Diameter 2.5 cm (1 inch) Only anterior 1/6 visible Lies in bony orbit Surrounded by a protective cushion of fat

some pictures…

Cataract (opaque lens)

The eye is an optical device: predominantly the lens (to a lesser degree, not shown here, the cornea also) Note: images are upside down and reversed from left to right, like a camera Resting eye set for distance vision: parallel light focused on retina Resting eye doesn’t see near objects because divergent rays are focused behind retina Lens accommodates (becomes rounder) so as to bend divergent rays more sharply, thereby allowing convergence on the retina

Photoreceptor neurons signal bipolar cells, which signal ganglion cells to generate (or not) action potentials: axons run on internal surface to optic nerve which runs to brain *Know that axons from the retina form the optic nerve, CN II

Photoreceptors: 2 types Rod cells More sensitive to light - vision permitted in dim light but only gray and fuzzy Only black and white and not sharp Cone cells High acuity in bright light Color vision 3 sub-types: blue, red and green light cones *Know that rods are for B & W and cones are for color

One of the Ishihara charts for color blindness Commonly X-linked recessive: 8% males and 0.4% females

The Ear Parts of the ear Outer (external) ear Middle ear (ossicles) for hearing) Inner ear (labyrinth) for hearing & equilibrium

Skeletal muscles of middle ear When loud, muscles contract, limiting vibration and dampening the noise

Inner ear = bony “labyrinth” of 3 parts Cochlea - hearing Vestibule - equilibrium Semicircular canals - equilibrium In petrous part of the temporal bone Semicircular canals____ Filled with perilymph and endolymph fluids Vestibule___________ Cochlea_______________________

Smell (olfaction) Olfactory epithelium in roof of nasal cavity Has millions of bipolar neurons = olfactory receptor cells Only neurons undergoing replacement throughout adult life

TASTE Taste buds: mostly on tongue Two types Fungiform papillae (small, on entire surface of tongue) Circumvallate papillae (inverted “V” near back of tongue)

Types of taste Sweet Sour Salty Bitter Glutamate (MSG) Gustatory (taste) pathway to brainstem & cerebral cortex via two cranial nerves: VII (Facial n.) – anterior 2/3 of tongue IX (Glossopharyngeal n.) – posterior 1/3 tongue and pharynx

Disorders of the nervous system Meningitis- inflammation of the linings of the brain and spinal cord Encephalitis- inflammation of the brain Epilepsy-seizure disorder. Excessive discharge from neurons. 1 in 200 suffer. Grand mal or petit mal seizures Cerebral palsy- disturbance in voluntary muscular action Parkinson’s –decreased neurotransmitter MS multiple sclerosis- autoimmune where the myelin is stripped.