Nervous System (SENSES :red_flag: (Types of Receptors based on stimulus…
Types of Receptors
Stimulus origin from internal organs
(e.g. digestive tube, bladder, lungs)
Monitor stimuli (changes in chemical concentration, taste stimuli, stretching of tissues, temperature).
Cause us to feel visceral pain, nausea, hunger, fullness.
Stimulus origin from muscles/ musculoskeletal organs
(e.g. skeletal muscles, tendons, joints, ligaments)
Monitor degree of stretch of these organs and send input on body movements to the CNS
Stimulus origin from environment
Located at or near body surface. Include receptors for touch, pressure, pain, and temperature in the skin & most receptors of the special sense organs.
Types of Receptors
based on stimulus type
Respond to chemicals in solution (e.g. chemicals tasted or smelled) and to changes in blood chemistry.
In the eye. Respond to light.
Respond to temperature changes
Respond to harmful stimuli that result in pain.
Respond to mechanical forces (touch, pressure, stretch, vibrations)
A specific type of mechanoreceptor
The eye components and visual pathways
The eye components
3 tunics of the eye
Nourishes the other layers. Deeply pigmented. Absorbs light and prevents scattering.
(a muscle that changes the shape of the eye).
Neural layer. Photoreceptors.
White, dense CT, protective, anchor for muscle.
Clear, transparent- Allows light into the eye. Involved with focusing light on retina.
Rods and Cones
MANY. Sensitive to light. Tells black and white and dim light.
FEWER. Allow us to see color. Best in bright light.
Lens and Iris
Both responsible for focusing light.
Posterior to iris. Focuses light on retina.
Anterior to lens. Intrinsic muscle. A sphincter muscle- dilates and contracts.
Other parts of the eye
"Precise posterior pole"
Exactly opposite your pupil
At the center of maculalutea. Clearest vision here.
"Blind spot" No photoreceptors
Posterior and Anterior Cavities/Segments
Largest segment/cavity- Everything posterior to lens and ciliary. Filled with vitreous humor. Supports retina and lens. Gel-like. Maintains normal pressure.
Filled with aqueous humor which nourishes the lens and cornea. Also maintains normal intraocular pressure.
Between cornea and iris
Between iris and lens
Path of light as it passes through the eye to the retina
Path of nerve impulses from the retina through the optic nerve, optic chiasm, and optic tract to the brain
RETINA-OPTIC NERVE-OPTIC CHIASM-OPTIC TRACT-MIDBRAIN-THALAMUS-PRIMARY VISUAL CORTEX IN OCCIPITAL LOBE
Olfaction components and pathway
Roof of nasal cavity (superior nasal conche)
Pseudostratified columnar epithelium w/olfactory sensory neurons
OLFACTORY RECEPTORS-OLFACTORY SENSORY NEURON W/IN THE OLFACTORY BULB-OLFACTORY TRACT- then to 2 places at once
Primary olfactory cortex in temporal bone
Gustation components and pathway
Tongue, inner cheeks, posterior wall of pharynx (throat), and epiglottis.
3 that transmit taste information from tongue to brain.
Glossopharyngeal nerve- IX
Vagus nerve- X
Path of nerve impulses from the gustatory receptors to the brain
3 FACIAL NERVES GO TO- MEDULLA OBLONGATA-THALAMUS-GUSTATORY CORTEX IN THE INSULA
Ear components and pathway
Gather, funnel, and amplify sound waves
Shell-shaped projection that surrounds the external acoustic meatus. Most is elastic cartilage covered with skin.
External acoustic meatus
Short tube from the auricle to the eardrum.
Tympanic membrane/ eardrum
Forms boundary between the external and middle ears
COCHLEAR BRANCH OF CN VIII (the vestibulocochlear nerve)-- MEDULLA OBLONGATA-- PONS -- MIDBRAIN -- THALAMUS -- PRIMARY AUDITORY CORTEX IN TEMPORAL LOBE
Nervous System Organization
PNS main structures and functions
Be sensitive to stumuli and send information toward the CNS. Serve as communication lines that link all regions of body to CNS.
Spinal nerves- Carry signals to and from spinal cord.
Ganglia- Areas where the cell bodies of neurons are clustered.
Cranial nerves- Carry signals to and from brain.
The sensory innervation of the outer tube: Skin, body wall, and limbs.
General: Touch, pain, pressure, vibration, temperature, and proprioception from the skin, body wall and limbs.
Special: Hearing, equilibrium, vision.
Stimulates contraction of skeletal muscles. "Voluntary nervous system."
CNS main structures and functions
Receive, process incoming signals, and responds.
Brain and spinal cord
Involuntary innervation of inner tube i.e. smooth muscle, cardiac muscle and glands; as well as some outer tube structures e.g. arrector pili muscle, smooth muscle in the vessels, and sweat glands.
3 Structural types of neurons
2 processes that extend on opposite sides from cell body: 1 is a fused dendrite, the other an axon. Very rare neurons occur in some special sensory organs (e.g. inner ear, olfactory epithelium of nose, retina of eye).
Short. single process that emerges from cell body and divides/forms central and peripheral processes., which together comprise an axon.
Have more than 2 processes (usually numerous dendrites and one axon). 99% of neurons in body.
3 Functional types of neurons
Motor (efferent) neurons
Most are multipolar. Cell bodies will be in CNS usually and travel to muscle and glands (to contract and secrete).
Sensory (afferent) neurons
Majority are unipolar. Bipolar in special senses. Cell bodies located in ganglia of PNS.
or association neurons
Only in CNS between neurons. Multipolar. Most abundant of all neurons in body (99.98%)
Major components of a neuron
Chromatophilic substance (Nissl bodies)
Clusters of free ribosomes and rough ER.
Function= renew the plasma membrane and protein within the cytosol.
Cone-shaped region of the cell body where axon arises from.
Makes ribsosomes. All but smallest neurons have.
Processes that branch from the cell body. Numerous. Function as receptive sites. Conduct electical signals toward cell body.
Only 1 per cell body. Impulse generators and conductors that transmit nerve impulses away from their cell body.
One nucleus per neuron
Or "soma" Single nucleus surrounded by cytoplasm. All neurons have a cell body. Most neuron cell bodies located in CNS. Receptive region.
When an axon branches (only occasional) -- Extend from axon at more or less right angles.
When an axon branches profusely at its end.
The very end knobs.
Anatomy of Nervous System
A bundle of axons
An insulating layer that covers some axons
Part of the neuron that carries a signal
Fibrous CT. Surrounds each fascicle.
Tough, fibrous CT. Surrounds nerve.
Bundle of axon fascicles.
4 of CNS; 2 of PNS.
Simple cuboidal/simple columnar epithelium. Cilia keeps CSF moving. Lines spaces with cerebrospinal fluid called ventricles.
in PNS. Found in ganglia. Surround neuron cell body. Structurally supportive. Regulates the exchange of materials in/out of neuron.
In CNS. Wrap their cell processes around the thicker axons producing the myelin sheath.
In CNS. Phagocytes that wander and monitor. Remove microbes and damaged nerve tissue.
In CNS. Most numerous glial cell. Many processes that contact neurons and capillaries. Supports neurons. Help maintain appropriate chemical environment.
Make myelin sheath in PNS.