THE BRAIN AND FIVE SENSES BRAIN- responsible for overseeing the daily operations of the human body and for interpreting the vast amount of information recieves.the adult human body brain weighs an average of 1.4 kg or about 2% of the total body weight.
The Brain is the main switching unit of the central nervous system;it is place to which impulses flow and from which impulses originate.
Spinal Cord provides the link between the brain and the rest of the body
THE BRAIN HAS THREE MAIN PARTS
-the brain is protected by bony covering called the SKULL
Wrapped in three layers of connective tissue called the MENINGES.
The innermost layer which covers surface of the brain is the PIA MATER.
The ARACHNOID is thin,elastic,weblike layer between the PIA MATER and DURA MATER.
The outer layer called the DURA MATER composed of thick connective tissue.
CEREBROSPINAL FLUID –space filled between the pia mater and the arachnoid .
CSF –is a clear liquid that protects the brain from mechanical injury by acting as schock absorber.
VENTRICLES –Cerebrospinal fluid that separates the middle and inner meninges and fills four interconnected or cavities in the brain.
In order that brain perform its functions must have constant supply of food and oxygen.
PARTS OF THE BRAIN
THE CEREBRUM – control center of the brain
Largest and most prominent part of the human brain.Brain is the cerebrum 85% OF THE WEIGHT OF HUMAN BRAIN.
Responsible for all voluntary activities of the body,site of INTELLIGENCE,LEARNING AND JUDGEMENT.
It functions in language,conscious,thought,memory,personality development,vision and other sensations.
-The left and the right cerebral hemispheres.
-There is a DEEP GROOVE that separates the two hemisphere- this are connected in the region known as CORPUS CALLOSUM
-The right and left cerebral hemispheres are linked by a bundle of neurons called a TRACT.
-It contains thick layers of unmyelinated neurons which look gray(GRAY MATER)
LOBES –These lobes are named for the skull bones-FRONTAL,PARIETAL,TEMPORAL AND OCCIPITAL LOBES.
Scientist have discovered that the left side of the body SENDS sensations to the right hemisphere of the cerebrum and the right side of the body send its sensations to the left hemisphere.
The right hemisphere associated with creativity and artistic ability while the left hemisphere with analytical and mathematical ability.
Sometimes blood vessels in the brain blocked by blood clots causing disorder called stroke.
Two surfaces of cerebrum
FOLDED OUTER SURFACE-CEREBRAL CORTEX and consists of GRAY MATER(unmyelinated neuron)
INNER SURFACE –CEREBRAL MEDULLA –made up of bundles of MYELINATED AXONS . THE WHITE MATTER-MYLIN GIVES WHITE MATER COLOR.
Second largest part of the brain and is locate at the back of the skull.
COORDINATES MUSCLE MOVEMENT
CONTROLS BALANCE,POSTURE AND COORDINATION
Receives sensory impulses from muscles,tendons,joints,eyes and ears.
Processes information about position and controls posture by keeping skeletal muscles in a constan state of partial contraction.
This is a small CAULIFLOWER SHAPED STRUCTURE.
Function of the cerebellum is involuntary(NOT UNDER CONSCIOUS CONDITION).
CONNECTS THE BRAIN AND SPINAL CORD
Maintains life support,systems,consist of diencephalon,medulla oblongata,pons,and the midbrain.
CONTROLS VITAL BODY PROCESSESS.
UPPER BRAIN STEM- DIECENPHALON
LOWER BRAIN STEM – MEDULLA OBLONGATA
MEDULLA contains WHITE MATER-conducts impulses between the spinal cord and brain.-also controls involuntary functions that include breathing,blood pressure,heart rate,digestion,swallowing and coughing.
Reticular activating system or reticular formation(RAS) –other important part of the medulla- RAS- HELP to allert or awakens the upper parts of the brain,including the cerebral cortex.-also helps to control respiration and circulation
just above the medulla,the brainstem enlarges to form pons and it MEANS BRIDGE,mostly white mater that link bet the cerebral cortex and the cerebellum.
Midbrain- above the pons and the smallest division of the lower stem-areas involved hearing and vision.
DIENCEPHALON(UPPER BRAIN STEM)
Thalamus and hypothalamus-bet. Brain stem and cerebrum
Thalamus- gray matter serves as switching station for sensory input with the exception of smell.
It is the relay station of the brain stem where sensory pathways in the spinal cord and brain stem form synapses on their way to cerebral cortex.
Hypothalamus-below the thalamus – control center for hunger,thirst,fatique,anger and body temperature
Includes the thalamus and the hypothalamus some deeper parts are the cerebral cortex and the temporal lobes- an plays an important role in emotions,memory and motivation
The seat of emotional interpretation.
Sensory receptors react directly to stimulation from the environment.
Sense organs-receive information from the environment.
Examples of stimulation are ( LIGHT, SOUND,MOTION,CHEMICAL PRESSURE, PAIN OF CHANGES IN THE TEMPERATURE.
ARE NEURON THAT IS SPECIALIZED TO DETECT STIMULUS THEY RESPOND TO:
Mechanoreceptors- respond to movement,pressure and tension
Photoreceptors (RODS AND CONES)-respond to variations to light.
Chemoreceptors-respond to chemicals
Thermorecptors-respond to changes in temperature
Pain receptors-respond to tissue damage-PAIN
MOST FAMILIAR SENSE ORGANS ARE THE EYES,EARS,NOSE,SKIN AND TASTE BUDS
THE RECEPTORS CONVERT THE ENERGY of a stimulus into an electrical energy that can travel in the NERVOUS SYSTEMS
Messages from sense organs to CNS are in the form of Nerve impulses.
Hearing and Balance
EAR is really two sense organ in one.not only detect sound waves also senses the position of the head whether it is still moving in a straight line or rotating.
High –pitched-faster variation
Consists of the visible fleshly part helps to collect sound and funnel into the AUDITORY CANAL(CONNECTS THE EXTERNAL EAR) with the tympanic membrane also called eardrum.
The AUDITORY CANAL- contains small hair and wax producing glands that prevent foreign objects from entering the ear.
Extends into the bone of the head and stops at the eardrum
Sound variations strike the eardrum and transmitted into three tiny bones.the malleaus(HAMMER) incus (ANVIL) and STAPES(stirrup)
THE STIRRUP TRANSFERS THE VIBRATIONS TO A THIN MEMBRANE CALLED OVAL WINDOW.
This membrane transmits the vibrations to the cochlea which begins the INNER EAR.
The COCHLEA IS snail shaped consisting of fluid filled chambers that are separated by membranes.
Organ of corti- middle chamber
These nerve impulses are carried to the brain by the AUDITORY OR ACOUSTIC NERVE
The ears also contain structures for detecting stimulus that make us aware of our movement and allow us to maintain our BALANCE.
LOCATED WITHIN THE INNER EAR JUST ABOVE THE COCHLEA ARE THREE TINY CANALS THAT LIE AT THE RIGHT ANGLES TO EACH OTHER –semicicular canals because they each make half a circle.
The semicircular canals and two tiny sacs located behing them helf us to sense balance or equilibirum.
ARE TINY RAINS OF CALCIUM CARBONATE AND PROTEIN.
-The sense organ we use to sense light is the eyes.
Composed of three layers- outer layer-consists of the sclera and cornea-middle choroid,ciliary body and iris-inner layer retina
SCLERA ( white of the eye)-MAINTAIN SHAPE OF THE EYE AND PROVIDES ATTACHEMENT FOR THE MUSCLES THAT MOVE THE EYE.
Cornea- front of the eye and forms a transparent layers and the part of the eye that enters light.
AQUEOUS HUMOR- JUST INSIDE THE CORNEA AND A SMALL CHAMBER FILLED WITH FLUID.
Choroid – back of the chamber ,contains blood vessels of the eye,becomes a disk-liske structure-IRIS
DIAPHRAGM(iris)portion of the eye that gives your eye its color and control the amount of light entering the eye by altering the diameter of the pupil
PUPIL – middle of the iris ,a small opening through which light enters the eye.-black disk in the center of the eye-regulate the size of the pupil controlling the amount of light to enter the eye.
Behind the iris-light is focused by the lens which cahnges shape when pulled by muscles around its edges.
Crystalin-cells that form the lens contain special protein and is almost transparent and allows light to pass through.
VITREAL CHAMBER-behind lens
VITREOUS HUMOR-Transparent jelly-like fluid
CONVERT light energy into impulses that are carried to the CNS.
CONTAIN PIGMENT CALLED rhodopsin-respond to wavelenghts of light.
TWO TYPES OF PHOTORECEPTORS
1.RODS –sensitive to all colors of light do not distinquish different colors.
2. CONES –sensitive than rods,do not respond differently to llight of different colors,producing color vision
Impulses leave the eye by way of optic nerve and carried part of the brain known as the optic lobe or occipital lobe-which interprets the visual images and provides information about the external world.
The sense of smell is a chemical sense responsible of smell called the olfactory receptors.
Located in the upper part of the nasal cavity
Chemorecptors contain cilia that extend into the air passages of the nose and react to chemicals in tha air.chemicals that come into contact with the chemoreceptors stimulate them causing impulses to be sent to the brain by the OLFACTORY NERVE
The sense of taste is a chemical sense
Stimulated by the chemicals called chemoreceptors
The sense organ detects taste.taste are the taste buds not the tonque.
Most 10,000 taste buds are embedded between bumps called PAPILLAE on the tonque but can also found on the rrrof of the mouth,on the lips and in the throat.
All regions of the body are sensitive to touch
SKIN - largest sense organs of the skin
mechanoreceptors – located throughout the skin make it posible to sense of touch,pressure and tension.
TWO TYPES OF OF RESPOND;
THERMORECEPTORS –respond to touch
MECHANORECEPTORS –respond to tissue damage which causes pain receptors.