Nervous system

Sensory – detect changesSensory – detect changes

Integrative – make decisionsIntegrative – make decisions

Responsive - take actionResponsive - take action

Types of nerves

Sensory – gather information; take it to the Sensory – gather information; take it to the brainbrain

Associative/interneurons – connect other Associative/interneurons – connect other neurons, process informationneurons, process information

Motor – carry impulses to Motor – carry impulses to effectors effectors (muscles or glands) where action is taken(muscles or glands) where action is taken

Divisions CNS – brain and spinal cordCNS – brain and spinal cord PNS – nerves running to and from the CNSPNS – nerves running to and from the CNS

Somatic NS – all sensory, and motor nerves to Somatic NS – all sensory, and motor nerves to musclesmuscles

Autonomic NS – to visceral organs and skinAutonomic NS – to visceral organs and skinSympathetic – originate in the thoracic and Sympathetic – originate in the thoracic and

lumbar areaslumbar areasParasympathetic – originate in the brain, Parasympathetic – originate in the brain,

cervical or sacral areascervical or sacral areas

The sympathetic and parasympathetic often The sympathetic and parasympathetic often have opposite actions on organs. One have opposite actions on organs. One stimulates an increase while the other stimulates an increase while the other causes a decrease. Homeostasis.causes a decrease. Homeostasis.

Neurotransmitters can be Neurotransmitters can be Excitatory – trigger nerve impulsesExcitatory – trigger nerve impulses Inhibitory – prevent nerve impulsesInhibitory – prevent nerve impulses

Structures found along nerves in the PNS

Ganglion – enlarged spot along a nerve that Ganglion – enlarged spot along a nerve that houses somas for sensory neurons outside houses somas for sensory neurons outside the CNSthe CNS

Plexus – a spot where many nerves (or Plexus – a spot where many nerves (or blood vessels) connect to one anotherblood vessels) connect to one another

Nerve pathway

A route traveled by an impulse as it travels A route traveled by an impulse as it travels through the nervous systemthrough the nervous system

The more often this path is traveled, the The more often this path is traveled, the more stable it becomes, new connections more stable it becomes, new connections are memories; reinforcing them makes a are memories; reinforcing them makes a memory stronger, able to be recalled easiermemory stronger, able to be recalled easier

Reflexes

Automatic, unconscious responses to Automatic, unconscious responses to changeschanges

Help maintain homeostasis (heart rate, Help maintain homeostasis (heart rate, breathing rate, digestion, blood pressure)breathing rate, digestion, blood pressure)

Automatic actions (coughing, sneezing, Automatic actions (coughing, sneezing, swallowing, vomiting)swallowing, vomiting)

Reflex Arc - Consists of sensory neuron, reflex center, motor neuron, effector

Reflex Arc cont.

1. A sensory neuron is stimulated – ex. Hot 1. A sensory neuron is stimulated – ex. Hot stove, rubber hammer on tendon stimulates stove, rubber hammer on tendon stimulates stretch receptor in musclestretch receptor in muscle

2. Impulse travels along sensory (afferent) 2. Impulse travels along sensory (afferent) neuron to the spinal cordneuron to the spinal cord

3. In the spinal cord the sensory neuron 3. In the spinal cord the sensory neuron stimulates several neuronsstimulates several neurons

Reflex Arc cont.

4. An impulse is immediately sent down an 4. An impulse is immediately sent down an efferent motor neuron to the muscle. Ex: efferent motor neuron to the muscle. Ex: bicep jerks hand back, leg kicksbicep jerks hand back, leg kicks

Simultaneously, a message is sent to the Simultaneously, a message is sent to the brain registering what happenedbrain registering what happened

* brain is NOT involved in the decision to * brain is NOT involved in the decision to movemove

Types of reflexes

Monosynaptic – sensory neuron connects Monosynaptic – sensory neuron connects directly to motor neuron – knee jerkdirectly to motor neuron – knee jerk

Polysynaptic – sensory and motor neurons Polysynaptic – sensory and motor neurons are connected by associative neurons – hot are connected by associative neurons – hot stove reactionstove reaction

The Brain – 3 major parts

Cerebrum – largest part of brain, has sensory Cerebrum – largest part of brain, has sensory areas, motor areas and is involved in higher areas, motor areas and is involved in higher thinkingthinking Folded surface allows more cells; grey matter Folded surface allows more cells; grey matter

on the surface is somas, deeper white matter is on the surface is somas, deeper white matter is axonsaxons

Gyri are hills, sulci are valleysGyri are hills, sulci are valleys Corpus Callosum made of axons connects the 2 Corpus Callosum made of axons connects the 2

sides of the brainsides of the brain

Cerebellum

Smaller, posterior and inferior to cerebrumSmaller, posterior and inferior to cerebrum Consists of smaller foldsConsists of smaller folds Coordinates movementsCoordinates movements Operates below the level of consciousnessOperates below the level of consciousness

Ventricles – spaces within the brain filled with cerebrospinal fluid

Brain Stem

Anterior to cerebellum, connects to spinal cordAnterior to cerebellum, connects to spinal cord Midbrain – most superior portion, connects lower Midbrain – most superior portion, connects lower

brain to cerebrumbrain to cerebrum Pons – inferior to midbrain, links cerebellum and Pons – inferior to midbrain, links cerebellum and

cerebrumcerebrum Medulla Oblongata – most inferior part of brain, Medulla Oblongata – most inferior part of brain,

controls breathing, heart rate and blood pressurecontrols breathing, heart rate and blood pressure

Cranial nerves There are 12 pairs of cranial nerves that come There are 12 pairs of cranial nerves that come

from the brain. from the brain. Pair I are the Olfactory nerves lead to the nose. Pair I are the Olfactory nerves lead to the nose.

(smell)(smell) Pair II are the optic nerves that lead to the eyes. Pair II are the optic nerves that lead to the eyes.

(vision)(vision) Pair VIII are the vestibular-cochlear nerves which Pair VIII are the vestibular-cochlear nerves which

lead to the ear. (balance and hearing)lead to the ear. (balance and hearing) The other pairs are a combination of sensory and The other pairs are a combination of sensory and

motor to the head, neck and trunk, including the motor to the head, neck and trunk, including the vagus nerve (X) to the heart.vagus nerve (X) to the heart.

Spinal cord

Slender nerve column that passes downward from Slender nerve column that passes downward from the brain into the vertebral columnthe brain into the vertebral column

Consists of 31 segments, each having a pair of Consists of 31 segments, each having a pair of spinal nerves that branch out to various body parts spinal nerves that branch out to various body parts and connect them with the CNSand connect them with the CNS

A core of gray matter arranged in “horns” A core of gray matter arranged in “horns” surrounded by white matter that has ascending and surrounded by white matter that has ascending and descending tracts of axons.descending tracts of axons.

Conduct nerve impulses and serve as a center for Conduct nerve impulses and serve as a center for reflexes.reflexes.

Meninges - the coverings of the CNS

Pia materPia mater – a delicate covering on the – a delicate covering on the surface of the brain which contains blood surface of the brain which contains blood vesselsvessels

Arachnoid mater Arachnoid mater – spiderweblike covering – spiderweblike covering which cushionswhich cushions

Dura materDura mater – a much tougher almost – a much tougher almost leathery coveringleathery covering

Blood-brain barrier

There is no blood actually within the brain There is no blood actually within the brain or spinal cordor spinal cord

Nutrients are carried by cerebrospinal fluidNutrients are carried by cerebrospinal fluid

Sight and the Eye – the orbit Eyelids – protect eye from debris, clean and Eyelids – protect eye from debris, clean and

lubricate with each blinklubricate with each blink Extrinsic muscles – 3 pairs move eyeball Extrinsic muscles – 3 pairs move eyeball

up, down; side to side; and twist slightlyup, down; side to side; and twist slightly Lacrimal glands – located above eye, Lacrimal glands – located above eye,

lateral; make tears that wash across surface, lateral; make tears that wash across surface, contain lysozyme; are collected incontain lysozyme; are collected in

Lacrimal ducts – medial lower corner of Lacrimal ducts – medial lower corner of eyelid; lead to nasal passageseyelid; lead to nasal passages

Structure of eye

Sclera – white of the eye, has blood vesselsSclera – white of the eye, has blood vessels Conjunctiva – on surface of scleraConjunctiva – on surface of sclera Cornea – clear, smooth surface, light passes Cornea – clear, smooth surface, light passes

throughthrough Aqueous humor – clear fluid posterior to Aqueous humor – clear fluid posterior to

corneacornea Iris – colored part of eye, actually a muscle Iris – colored part of eye, actually a muscle

that controls the amount of light coming inthat controls the amount of light coming in

Structure of eye cont.

Pupil – hole in the center of the iris Pupil – hole in the center of the iris Lens – posterior to pupil; hard but flexible, Lens – posterior to pupil; hard but flexible,

bends light as it passes through to focus it bends light as it passes through to focus it on the back of the eye; loses flexibility as on the back of the eye; loses flexibility as you ageyou age

Suspensory ligaments/ciliary muscles – pull Suspensory ligaments/ciliary muscles – pull on the lens to slightly change its shape, on the lens to slightly change its shape, focus for far or near, focus for far or near,

Structure of eye cont.

Vitreous humor – clear gel posterior to lens Vitreous humor – clear gel posterior to lens that fills the cavity inside the eyeballthat fills the cavity inside the eyeball

Choroid coat – pigmented layer just deep to Choroid coat – pigmented layer just deep to the sclera at the back of the eye. Absorbs the sclera at the back of the eye. Absorbs extra light. This is reflective in many extra light. This is reflective in many nocturnal speciesnocturnal species

Retina – at the back of the eye

Layers in order that light passes throughLayers in order that light passes through Nerve fibersNerve fibers Connecting neuronsConnecting neurons Receptor cellsReceptor cells

Rods – detect light and dark, rhodopsinRods – detect light and dark, rhodopsinCones – detect color; red, green, blueCones – detect color; red, green, blue

Choroid coat – light stops hereChoroid coat – light stops here

Retina cont.

Fovea centralis– area where most of light Fovea centralis– area where most of light hits, pit with densely packed coneshits, pit with densely packed cones

Blind spot – the area where the optic nerve Blind spot – the area where the optic nerve leaves the eye, no receptor cellsleaves the eye, no receptor cells

Optic nerve

Nerves from each eye come together at the Nerves from each eye come together at the chiasma where info from the left side of chiasma where info from the left side of each eye goes one way, and from the right each eye goes one way, and from the right goes the other.goes the other.

Travels to the visual center of the cerebrum Travels to the visual center of the cerebrum at the rear of the brainat the rear of the brain

The Ear – hearing and balance

External Ear – External Ear – auricleauricle – funnels sound into ear – funnels sound into ear canalcanal

Tympanic membrane – eardrum that vibrates from Tympanic membrane – eardrum that vibrates from sound wavessound waves

Middle earMiddle ear Ossicles – 3 small bones that amplify sound Ossicles – 3 small bones that amplify sound

waveswavesMalleus (hammer), incus (anvil) and stapes Malleus (hammer), incus (anvil) and stapes

(stirrup)(stirrup)

Inner ear

Oval window – moved by stapes, pushes on fluid Oval window – moved by stapes, pushes on fluid of inner earof inner ear

Cochlea – snail shaped organ lined with hair cells Cochlea – snail shaped organ lined with hair cells that vibrate at specific frequencies. The higher the that vibrate at specific frequencies. The higher the sound, the faster the vibrationsound, the faster the vibration With age, the hairs which register high pitches With age, the hairs which register high pitches

become damaged, and there is some hearing become damaged, and there is some hearing loss. Loud or repeated noises can do permanent loss. Loud or repeated noises can do permanent damage.damage.

Balance and position

The semicircular canals are part of a labyrinth The semicircular canals are part of a labyrinth Dynamic equilibrium registers movement Dynamic equilibrium registers movement Static equilibrium registers position at restStatic equilibrium registers position at rest Small grains of calcium carbonate called Small grains of calcium carbonate called

otoliths embedded in a gel otoliths embedded in a gel move against hair cells in the canalsmove against hair cells in the canals