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Components of a Reflex Arc

Sensory Receptor
Sensory Neuron
Integrating center
Motor neuron

Patellar reflex

Hammer strikes tendon
Tendon bends and stretches attached muscle
Muscle contracts to relieve stretch

Flexor and Crossed Extensor Reflexes

Paired reflex

Corneal reflex

Mediated by Trigeminal Nerve V- causes the blinking action

Pupillary light and consensual reflex

Paired reflexes, shining light leads to pupil constriction in both eyes
Pupillary reflex- ipsilateral
Consensual reflex- contralateral side

Ciliospinal reflex

SNS causes vasodilation of the pupil on the same side as a stimulus

Salivary reflex

Mediated by cranial nerve Facial VII, and Glossopharangeal IX. Stimulate glands to increase saliva production at the sight or smell of food

Somatic Sensation

General- Originate form either sensory somatic receptors (skin or skeletal muscles) or visceral somatic receptors
Special- From special sense organs like eye, inner ear, nose, taste buds

General somatic receptors

Modified sensory nerve cell endings (sensory receptors and neurons are on the same cell)
(Sensory neurons are house in special places and have cells that communicate with the sensory neurons)

Meissner's Corpuscles

Location: Dermal papillae of hairless skin
Stimuli: Touch and pressure

Hair Root Plexus

Location: surrounds hair follicles
Stimuli: Touching hair

Pacinian Corpuscles

Location:Subcutaneous and submucosal tissue, joints, tendons, and muscles
Stimuli: Touch and pressure

Merkel Discs

Location: Associated with Merkel cells in stratum basale layer of epidermis
Stimuli: Touch and pressure

Ruffini's Corpuscles

Location: Dermis, ligaments, tendons
Stimuli: Stretching of digits and limbs

Muscle spindles

Location: Most skeletal muscles
Stimuli: Changes in muscle length

Tendon organs

Location: junction of tendons and muscles
Stimuli: changes in joint position and movement

Warm receptors

Location: Dermis
Stimuli: Thermoreceptor of temps between 32-48 C

Cold receptors

Location: Dermis
Stimuli: Thermoreceptor of temps 10 to -40 C


Location: every body tissue
Stimuli: pain receptors, harmful stimuli

Palm vs. Calf

Palm- has a smaller receptor field i.e. a greater density of receptors
Calf- larger receptor field has less density of receptors

Tactile localization

Has motor and sensory components along with showing a size of a receptor field


An area of skin that is mainly supplied by a spinal nerve


2nd greatest cause of blindness due to increased pressure in the eye
Aqueous humor builds up due to angle blockage
Open angle (chronic), Angle closure (acute), Congenital (from birth)

Layers of the eyeball

Fibrous Tunic
Middle vascular tunic
Inner retina

Fibrous tunic

Cornea- transparent portion
Sclera- tough, white portion with the sclera venous sinus (junction of cornea and sclera)

Middle vascular tunic

Iris and pupil
Ciliary body

Ciliary body

Ciliary muscle- controls the shape of the lens
Ciliary processes- folds that protrude from the ciliary body toward the lens, secretes aqueous humor


Most posterior part of the vascular tunic
Contains blood vessels to nourish retina

Inner retina

Ora serrata- serrated boundary between ciliary muscle and the retina
Pigmented outer later and neutral inner layer that contain photoreceptors and associated neurons

Initial segment

Also the trigger area, the beginning of an axon where the action potential is generated


Covers neurons and blood vessels to keep them in place, guides neurons during development, and form a blood brain barrier
In the CNS


Form myelin sheaths around axons
In the CNS

Schwann Cells

Form myelin sheath around axons
In the PNS

Satellite cells

Give support to PNS neurons and regulate their chemical environment

White matter

Groups of myelinated axons in the CNS

Four regions of the brain

1. Cerebrum
2. Diencephalon
3. Brain stem
4. Cerebellum

Basal ganglia

Areas of deep gray matter composed of paired nuclei (clusters of cell bodies in the CNS)

Corpus callosum

Commissural fiber tract that connects the hemispheres


Tract of arches association fibers

Internal capsule

Projection fibers that connect the cerebral cortex to the brain stem and spinal cord


Divided in half, connected by the intermediate mass
Serves as the central relay station


Included the pineal gland


Controls bodily functions, homeostasis, and has a hormonal function
Has infundibulum, pituitary glands, and mammillary bodies


Connects the pituitary gland to the hypothalamus

Mammillary bodies

Relay stations for taste and smell

The Brain Stem

Has the medulla oblongata, the pons, and the midbrain

Medulla oblongata

Respiratory and cardiovascular control center
Reflex centers for coughing, vomiting, and sneezing


Assist medulla in controlled breathing
Relays info to the diencephalon and the cerebrum


Has cerebral pundicles- (connects upper and lower brain area
Corpora quadrigemina- 4 colliculi


Regulates posture and balance
Smooths skilled muscle movements

Cranial meninges

Protect the brain
Dura (periosteal and meningeal), arachnoid, and pia mater

Choroid plexus

Tiny blood vessels that allow plasma to leak through

Interventricular foramen

Goes in between the lateral ventricles and the third ventricle

Cerebral aqueduct

Goes in between the third ventricle and the fourth ventricle

Flow of the CSF

1. Epdendymal cells of choroid plexus in lateral ventricles (filtered from blood plasma
2. Third ventricle
3. Fourth ventricle
4. Can either go to the medial & lateral apertures of 4th ventricle or the central canal of the spinal cord
5. Subarachnoid space of brain & spinal cord
6. Arachnoid villi
7. Superior sagittal sinus returns CSF to blood

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