Nervous System

Senses

Anatomy of Nervous System

Nervous system organization

Neurons

Receptors: detect stimuli
and send signals to the CNS

Based on stimulus type

Based on stimulus origin

Chemoreceptor

Interocepters

Proprioceptors

Exterocepters

Sensitive to stimuli outside the body. Ex: touch, pain, pressure, pain in skin.

Sensitive to stimuli from visceral organs. Ex: Changes in chemical concentration.

Located in the musculoskeletal organs. They send inputs on body movement to the CNS.

Photoreceptor

Thermoreceptor

Nocireceptor

Mechanoreceptor

-touch, pressure, stretch, vibrations, and even blood pressure detected by t he BARORECEPTOR.

Temperature changes

Chemical change in solution and changes in blood chemistry

Responds to light

-respond to harmful stimuli that result in pain.

Vision

Eye components

Visual pathway

Inner layer

Vascular layer

Fibrous layer

Cornea

Sclera

choroid

iris

Ciliary body

Optic nerve

retina

white layer that protects the eyeball and provides it with shape.

transparent layer through which light enters the eye.

ring of thick tissue that encircles the lens

colored part of the eye which has the pupil- a hole that allows light in.

highly vascular and pigmented membrane that helps nourish other parts in the eye

nerve that runs from eye to brain

Made of the outer pigmented layer and inner neural layer, it helps to absorb light and detect light with its photoreceptors.

lens

thick transparent disc that changes shape to allow focusing of light on retina

Segments

Anterior

Posterior

Anterior chamber

Posterior chamber

Filled with vitreous humor. Transmits light, helps support the neural layer and helps maintain pressure

between cornea and iris. contains aqueous humor that helps nourish the avascular lens and cornea.

between iris and lens

Cornea>Lens>Retina>Optic nerve>Optic chiasm> Optic tract> Midbrain>Thalamus>Primary visual cortex in the occipital lobe

Olfaction

Pathway

Roof of nasal cavity(olfactory sensory neurons)> Through Cribiform foramina> Olfactory bulb> Olfactory tract> Limbic region and primary olfactory cortex

Gustation

Pathway

Taste buds> 3 cranial nerves ( Facial, Glossopharngyeal, Vagus)> Medulla oblungata>Thalamus> Primary gustatory cortex in insula lobe

Hearing and equilibrium

auditory pathway

Outer ear(auricle) > External acoustic meatus> Ear drum> Middle ear> cochlea> Cochlear nerve and vestibulocochlear nerve> medulla oblungata> pons> midbrain>thalamus> primary auditory cortex in temporal lobe

Central nervous system

Peripheral nervous system

integrates sensory information and responds

Brain

Spinal cord

Gathers information and passes it on to the CNS.Includes the spinal nerves, the cranial nerves and ganglia.

Divisions

Afferent division

Efferent division

Visceral sensory

Somatic nervous system

Somatic sensory

Autonomic nervous system

General: Temperature, pressure, pain, touch in skin, body walls and limbs.

Special: Equilibrium, vision, hearing

Specific: Gustation, olfaction

General: stretch, pain, temperature, chemical changes and irritation in viscera.

motor innervations of all skeletal muscles

motor innervation of smooth muscle, cardiac muscle, and glands.

Nerve components

Glial cells- supporting cells

Axons

Connective tissue

carry signals away from the cell body. Some axons are covered in myelin sheath. A bundle of axons make a fascicle

Endoneurium

perineurium

epineurium

loose connective tissue that covers each axon

fibrous connective tissue that covers fascicles

tough fibrous connective tissue that covers the entire nerve

In the CNS

In the PNS

Astrocytes- most abundant cells that help to maintain a proper chemical environment. Their processes attach to axons and capillaries.

Microglia- smallest glial cells that act as phagocytes.

Ependymal cells- simple cuboidal epithelium that have cilia and microvilli. They help circulate the cerebrospinal fluids.

Oligodendrocytes- wrap their cell process around axons and produce myelin sheaths.

Satellite cells- surround neuron cell bodies within ganglia. they help regulate what goes in and out of the cell body.

Schwann cells- only wraps one axon and maybe even multiple times. They create the myelin sheaths.

Structural types

Functional types

Major components

Bipolar- has two processes that extend in opposite sides

Unipolar- has one short single process that emerges from cell body and then divides.

Multipolar - has more than two processes. Usually multiple dendrites and one axon

motor neuron- signals muscle cells or gland cells

Interneuron- lies between sensory and motor neuron or is completely confined to the CNS.

Sensory neuron- specialize in carrying information from sensory receptors

Neuron processes- dendrites and axons responsible for receiving and sending signals respectively. Axons arise in the axon hillock, may contain branches( axon collateral) and end at the axon terminal.

Cell body- contains nucleus and chromatophilic substance responsible for renewing membranes and proteins.

Synapse- although not a part of the neuron, its is the site where neurons communicate.