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the point where nerve signals pass from one neuron to another.
brings the signal to the synapse.
accept the neurotransmitter and are stimulated or inhibited.
Chemicals secreted by the end of an axon
Stimulates a muscle to contract or a neuron to fire an impulse
Acetylcholine- controls skeletal muscle action
Norepinephrine- creates a sense of well-being (low levels may lead to depression)
Dopamine- well-being (low levels associated with Parkinson disease
Serotonin- inhibitor, causes sleepiness
Caused by various stimuli:
Environmental changes affect the membrane potential by opening a gated ion channel
Meninges are membranes that cover the brain and the spinal cord
(outermost) dense, white connective tissue. The dura mater attaches to the inside of the skull and forms the inner periosteum of the skull bones. Extends into the vertebral canal
Thin, weblike membrane that lacks blood vessels
(between Arachnoid mater and Pia mater) contains cerebrospinal fluid (CSF)
(Innermost) thin, contains many nerves and blood vessels (nourish brain and spinal cord) Attached to nervous tissue
are specialized capillaries in the pia mater that secrete cerebrospinal fluid.
is a slender column of nervous tissue that is continuous with the brain and extends through the vertebral canal.
Originates when the brain stem leaves the skull at the foramen magnum
Terminates between the first and second lumbar vertebrae
Structure of the Spinal Cord
Consist of 31 segments, each of which gives rise to 1 pair of spinal nerves.
Cervical enlargement supplies nerves to the upper limbs
Lumbar enlargement supplies nerves to the lower limbs
At the Conus medullaris the spinal cord tapers into separate spinal nerves
Cauda equina- collection of nerve roots at the inferior end of the vertebral canal (means horse’s tail)
Primary motor areas are located in the gyri of the frontal lobe just in front of the central sulcus. They control voluntary muscles.
Broca’s area (motor speech area) is just anterior to the primary motor cortex. Controls complex muscle actions of the mouth, tongue and larynx (making speech possible).
Frontal eye field is located above the Broca’s area, and controls voluntary movements of the eyes and eyelids.
is located between the cerebral hemispheres and is superior to the brainstem.
is located below the Thalamus
The hypothalamus regulates:
Heart rate & arterial blood pressure
Water & electrolyte balance
Hunger & body weight
The movement of glandular secretions of the stomach & intestines
Sleep & wakefulness
Endocrine system function
Hypothalamus – maintain homeostasis
connects the brain to the spinal cord. It consist of the midbrain, pons and medulla oblongata.
is the most superior (and shortest) portion of the midbrain. It is located between the diencephalon and the pons
Contains reflex centers for eye and head movements
is a rounded bulge on the anterior portion of the brainstem. It separates the midbrain from the medulla
Contains centers that maintain the basic rhythms of breathing
is the inferior portion of the brainstem, and is located between the
Cardiac center – regulates heart rate
Respiratory center – regulate breathing
Vasomotor center – regulate blood pressure
Reflex centers for vomiting, coughing, sneezing & swallowing
pons and the spinal cord.
Parkinson Disease (PD) causes a degeneration of neurons in an area of the brainstem called the substantia nigra. This area is responsible for the production of the neurotransmitter dopamine. This means individuals with PD produce less dopamine.
Low levels of dopamine explain motor symptoms, such as muscle rigidity, off-balance stride, poor small-motor control, expressionless face, difficulty communicating and small handwriting.
Non-motor symptoms include depression, dementia, constipation, incontenance, sleep problems, dizziness
(I) Olfactory– sense of smell
(II) Optic– vision
(III) Oculomotor– eye movement
Largest of the cranial nerves
Conducts sensory impulses from the skin of the face and mucosa of the nose and mouth
Contain motor fibers that activate the chewing muscles
(VI) Abducens– turns the eyes outward
) Trochlear– eye movement
Activates the muscles of facial expression
Carries sensory impulses from the taste buds of the tongue
(VIII)Vestibulocochlear– sense of balance and hearing
(IX) Glossopharyngeal– promote swallowing & saliva production
(X) Vagus– Transmit impulses from the thoracic and abdominal organs, esophagus, larynx and pharynx to the brain
(XI) Accessory– Activate the shoulder movements
(XII) Hypoglossal– Control tongue movement and carry impulses to the tongue
Nerve plexus – complex networks formed by anterior branches of spinal nerves; fibers of various spinal nerves are sorted and recombined
Lies deep in the neck
Supply muscles and skin of the neck
Fibers (3,4,5 nerves) pass into the right and left phrenic nerves
Phrenic nerves conduct motor impulses to the muscle fibers of the diaphragm
C5 – T1
Lies deep within shoulders
Supply muscles of anterior arms and skin of forearms
Supply muscles of forearms and hands
Supply skin of hands
Supply muscles of forearms and muscles & skin of hands
Supply posterior muscles of arms and skin of forearms and hands
Supply muscles and skin of anterior, lateral and posterior arms
T12 – S5
Extend from lumbar region into pelvic cavity
Supply adductors of thighs
Supply muscles and skin of thighs and legs
Supply muscles and skin of thighs, legs and feet
Lobes of the Cerebrum
Frontal Lobe- Anterior portion of each hemisphere
Borders= (1) Central Sulcus (posterior) and (2) lateral Sulcus (inferior)
Parietal Lobe- behind the Frontal
Temporal Lobe- inferior to Frontal and Parietal
Occipital Lobe- Posterior portion of each cerebral hemisphere
Insula- located deep in the cerebrum. "Insulated" by the Frontal, Parietal and Temporal Lobes
Structure of the Cerebrum
Cerebrum is the largest part of the mature brain
Consist of 2 large cerebral hemispheres (right & left)
These hemispheres are connected by the corpus callosum
Cerebrum’s surface contains many convolutions called gyri (singular gyrus) separated by grooves
Sulcus = shallow to medium groove
Fissure = deep groove
Longitudinal fissure separates left and right hemisphere
Transverse fissure separates cerebrum and cerebellum
Sensory receptors: structures that are specialized to respond to changes in their environment
Five general receptors:
Chemoreceptors: receptors that are stimulated by changes in the concentration of chemical substances. Receptors associated with the senses of smell and taste
Ex. Chemoreceptors in internal organs can detect changes in the blood concentrations of substances including oxygen and glucose
Thermoreceptors: receptors sensitive to temperature changes.
Photoreceptors: receptors that respond to light intensity. Found only in the eye.
Sensory Receptors (cont.)
Nociceptors: pain receptors. Tissue damage stimulates pain
Mechanoreceptors: receptors sensitive to mechanical pressure such as touch, sound or muscle contraction.
Sense of Taste
Taste buds – the sensory receptor organs for taste located primarily on the surface of the tongue
Taste buds are scattered in the roof of the mouth, the lining of the cheeks and the walls of the pharynx
Taste buds are associated with elevated ridges called papillae
4 Basic Taste Sensations
Sweet receptors are located near the tip of the tongue. Ex. A child licking a lollipop rather than chewing it.
Sour receptors are located along the sides of the tongue – Acids (H+ ions) stimulate them
Salty receptors are located on the tip and sides of the tongue. Sodium ions stimulate the salt receptors.
Bitter receptors are located on the back of the tongue. Bitter is often associated with alkaloids such as nicotine, caffeine, quinine & morphine
Sense of Smell
Your sense of smell allows you to smell the scent of flowers
To identify the
smell of a rose, the brain analyzes over 300 odor molecules
The average person can discriminate between 4,000 – 10,000 different odor molecules
Much is unknown about exactly how we detect and discriminate between various odors
Researchers have discovered that an odor can only be detected in a liquid form
The clear mucus dissolves odor molecules that are not in watery form
The nose contains specialized sensory nerve cells or neurons, with hair-like fibers called cilia on one end
Each neuron sends a nerve fiber called an axon to the olfactory bulb, a brain structure just above the nose
If the mucus in your nasal passage becomes too thick, air and odor molecules can’t reach your olfactory receptor cells
The Sense of Hearing
The structures of the outer, middle and inner ear are involved in the sense of hearing
The inner ear also contains structures that provide for a sense of balance or equilibrium and hearing
Structures of the Ear
Auricle or pinna – directs sound waves into the ear. Part of the external ear.
External auditory meatus (canal) – part of the outer ear. Contains hairs and wax to help keep large, foreign objects, such as insects out of the ear.
External auditory canal or meatus – transmits sound waves to the tympanic membrane
Middle Ear Consists of:
Tympanic membrane – transmits sound waves to the malleus
Tympanic cavity – an air-filled space in the temporal bone that separates the external ear & internal ear
3 auditory ossicles: malleus, incus & stapes are attached to the wall of the tympanic cavity by tiny ligaments
Auditory Tube (Eustachian Tube)
Connects each middle ear to the throat
Allows air to pass between the tympanic membrane & the outside of the body by way of the throat (nasopharynx) & mouth
Equalizes pressure on both sides of the tympanic membrane
A complex system of intercommunicating chambers & tubes called labyrinth
Each ear has 2 regions:
Osseous labyrinth – bony canal in the temporal bone
Membranous labyrinth – tube within the
Between the osseous & membranous labyrinth is a fluid called perilymph, which the cells in the wall of the bony canal secretes.
The membranous labyrinth contains endolymph
The labyrinth consists of:
Cochlea – organ of hearing (Snail-like structure)
Vestibule - balance
Structures of the Eye
Sclera – white outer layer of the eyeball; provides shape
Iris – pigmented cells, regulate the diameter of the pupil
Retina – contains the rods and cones; photoreception
Lens – refracts light & focuses into fovea centralis
Pupil – allows light to enter the eye
The organ of hearing
Cochlea is divided into upper & lower compartments:
Scala vestibuli (upper): communicates with the scala tympani through a small opening called helicotrema
Scala tympani (lower): duct filled with perilymph
Cochlea duct – lies between the two bony compartments & is filled with endolymph
Organ of Corti
Terminal acoustic apparatus in the cochlea
Transducer that converts vibrations into nerve impulses
The organ of hearing
Rods – the dim receptors & peripheral vision receptors
Cones – the photoreceptors that operate best in bright light & color vision
Eyebrow – short thick hair to disperse sunlight & trap particles
Eyelids - movable folds of skin that protect the eyeball from airborne particles and desiccation
Eyelashes – two rows of numerous short hairs, protect the eyeball
Clinical Conditions of the Eye
Hyperopia – farsightedness. The eyeball is too short and the image is focused at a point behind the retina
Myopia – nearsightedness. The eyeball is elongated, and the image is focused at a point in the vitreous humor in front of the retina
Diplopia – double vision
Nightblindness – poor vision in dim light, caused by to not enough dietary vitamin A
Conjunctivitis – "pinkeye" inflammation of the eye that results in red irritated eyes due to bacteria (very contagious), viruses or allergies
Glaucoma – blockage of the drainage of aqueous humor
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