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Nervous system Beatrice Mwachugu (Senses (Ear components (Auditory pathway…
Nervous system Beatrice Mwachugu
Senses
Types of receptors based on origin of stimulus
Exteroceptors
stimulus originates from outside environment
Interoceptors
stimulus originates from internal organs
Proprioceptors
stimulus originates from muscles
Types of receptors based on the type of stimulus
Photoreceptor
sensitive to light
Thermoreceptor
sensitive to cold and warmth
Chemoreceptor
sensitive to chemicals
Nociceptor
sensitive to pain and danger
Mechanoreceptor
sensitive to touch
Baroreceptor
sensitive to blood pressure
Eye components
Fibrous layer
Sclera
Gives shape to the eye and anchors
Cornea
Allows light into the eye
Vascular layer
Choroid
Absorbs light and nourishes other layers
Inner layer
Retina
Absorbs light
Visual pathway
Cornea
pupil
lens
retina
optic nerve, optic chiasm, optic tract
midbrain
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Oflaction components
Olfactory epithelium
Olfactory sensory neuron surrounded by columnar supporting epithelial cells
Olfactory stem cells that form new olfactory sensory neurons
Olfactory cilia or hair that act as receptive structures for smell
Olfaction pathway
5) limbic region. Where smells elicit emotions
4) Olfactory tract (where mitral cells transmit impulses to limbic region
6) Olfactory cortex (processes olfactory information into perception of odor
3) Olfactory bulb (neurons called mitral cells synapse at the olfactory bulb.
2) Olfactory sensory neuron (has axons called filaments of the olfactory nerve which penetrate the cribriform to the olfactory bulb
1) Olfactory receptors receive information(smell) through the olfactory cilia
7)Orbitofrontal cortex (Where smells are analyzed and compared to other smells
Gustation Components
Gustatory epithelial cells and basal epithelial cells which generate impulses
Gustatory hair that contain saliva which has dissolved molecules that dissolve taste.
Basal epithelial cells which replenish cells by division process
Gustatory pathway
Sensory fibers that occur in the
Facial nerve (VII) carries taste impulses from the anterior of the tongue
Glossopharyngeal nerve (IX) caries sensations from the tongues posterior
Vagus nerve (X) carries tatse buds from epiglottis and lower pharnx
Solitary nucleus (Where synapse takes place)
Thalamus
Cerebal cortex in the gustatory area
Ear components
Pinna/auricle which gathers and amplifies sound waves
Auditory ossicles which transport sound vibrations from the ear drum to a fluid in the internal ear.
Tympanic membrane/eardrum which transports sound waves to the middle ear through vibrations
Cochlea transform sound into neural message
Pharyngotympanic tube which equalizes pressure around eardrum
Semi circular canals help keep your balance.
Auditory pathway
5)Thalamus
6)Primary auditory cortex
4)Inferior colliculus
3)Lateral lemniscus
2)Superior olivary nuclei
1) Cochlea nerve: where impulses pass through to the cochlea nuclei
Nervous system organization
CNS structures
Spinal cord
Brain
CNS function
Receives sensory signals ,interprets and dictates motor responses bases on experineces
PHS structures
Cranial nerves
Spinal nerves
PHS function
Serve as communication lines that link all regions of the body to the central nervous system
Components of nervous system
Motor /efferent which takes information away from the CNS
Sensory/afferent takes information from receptors to the CNS
Divisions of nervous system
Somatic motor
Voluntary movement which conducts impulses from the CND to the skeletal muscles
Autonomic motor
Involutary conducts impulses from CNS to cardiac muscles,smooth muscles and glands
Neurons
Components of neurons
Cell body
Where signals from dendrites are joined and passed on
Nucleus
stores DNA and controls cell activities
Nucleolus
Ribosome synthesis
Chromatophilic substance
Renew membranes of the cell and protein components
Axon hillock
where the axon joins the cell body
Dendrites
Receive information and transmit to the cell body
Axon
Transmits information from the cell body
Axon collaterals
Regulate cell firing pattern
Terminal arborization
Terminal boutons/axon terminals
Secretory region
Functional types of neurons
Sensory/Afferent
Carry impulses from the CNS to skeletal muscles
Motor/Efferent
Carry impulse away from the CNS to muscles and glands
Interneurons
Lie between motor and sensory and forms complex neuronal pathways
Structural types of neuron
Multipolar neurons
Many processes extended from the cell body with a single axon
Bipolar neurons
Have two processes extended from the cell body
Unipolar neurons
One process extends from cell body which forms central and peripheral processes
Anatomy of nervous system
Nerve components
Endoneurium
Encloses the schwann cells which surround the axons
epineurium
surrounds the whole nerve
Perineurium
Surrounds a fascicle
Blood vessels
Nourish axons and Schwann cells
Glial cells
Glial cell in CNS
Astrocytes
Control ionic environment
Signals increased blood flow through capillaries
Microglia
engulf invading microorganism or dead nerons
Ependymal
Have cilia that help to circulate cerebrospinal fluid
Oligodendrocytes
wrap their cell process on thicker axons
Glial cells in PNS
Satelite cells
Surround neuron cell bodies with ganglia
Schwann cells
form myelin sheaths and surrounds axons
Myelin sheaths
Form an insulating layer to prevent leakage of electrical current