Study Guide for BSC2085C Anatomy Physiology I

Control:
- Voluntary control of the body, primarily involving skeletal muscle movement.
Effectors:
- Only affects skeletal muscles.
Pathway:
- Consists of a single motor neuron that travels directly from the central nervous system (CNS) to the muscle.
Neurotransmitter:
- Acetylcholine (ACh) is released at the neuromuscular junction to stimulate muscle contraction.
Effect:
- Always results in excitation, leading to muscle contraction.
Sensory Input:
- Receives sensory information from somatic receptors located in the skin, muscles, and joints.

Control:
- Operates involuntarily, regulating visceral organ functions.
Effectors:
- Affects cardiac muscle, smooth muscle, and glands.
Pathway:
- Utilizes a two-neuron chain, comprising preganglionic neurons and postganglionic neurons.
Neurotransmitters:
- Releases Acetylcholine (ACh) and norepinephrine (NE) at different points in the pathway.
Effect:
- Effects can be either excitatory or inhibitory, depending on the type of receptor engaged.
Sensory Input:
- Gathers sensory information from visceral receptors located in the internal organs.

Origin:
- Thoracolumbar region of the spinal cord (specifically from T1 to L2).
Ganglia Location:
- Located near the spinal cord, either in the sympathetic trunk (chain) or in collateral ganglia.
Preganglionic fibers:
- Typically short in length.
Postganglionic fibers:
- Typically long, extending to target effectors.

Origin:
- Craniosacral region, specifically from cranial nerves III, VII, IX, X, and sacral segments S2 to S4.
Ganglia Location:
- Found near or within target organs, classified as terminal or intramural ganglia.
Preganglionic fibers:
- Longer than sympathetic division fibers.
Postganglionic fibers:
- Short in comparison to sympathetic fibers.

Sympathetic (Thoracolumbar):
- Known for the "fight-or-flight" response, which includes increasing alertness, heart rate, pupil dilation, and reducing digestive activity.
Parasympathetic (Craniosacral):
- Frequently termed the "rest-and-digest" system, promoting energy conservation and enhancing digestive motility and secretion.

Governs involuntary processes associated with:
  - Cardiac muscle
  - Smooth muscle
  - Glands
Homeostasis Maintenance:
- Works continuously without conscious awareness to regulate the internal environment.

Sympathetic:
- Increases heart rate (↑ HR), enhances blood flow to muscles (↑ blood flow), decreases digestive activity (↓ digestive activity), and causes pupil dilation.
Parasympathetic:
- Decreases heart rate (↓ HR), enhances digestive activity (↑ digestive activity), and causes pupil constriction.

Definition:
- Sympathetic and parasympathetic divisions usually have opposing (antagonistic) effects on the same organ systems, such as heart rate regulation.

Autonomic nervous system (ANS) neurons have the capacity to either excite or inhibit their target effectors, unlike somatic neurons that can only excite skeletal muscle.

Effector organs:
- Includes cardiac muscle, smooth muscle, and glands, explicitly excluding skeletal muscle from the ANS purview.
Visceral sensory input:
- Involves the ANS receiving signals from the internal organs.

Comparison of Reflex Types:
- Somatic reflexes (e.g., knee jerk) versus autonomic reflexes involved in visceral regulation.

Receptive Field:
- Defines the area monitored by a single sensory receptor.
Adaptation:
  - The diminishing responsiveness to a consistent stimulus over time.
  - Phasic Receptors:
    - Adapt quickly to stimuli (e.g., touch).
  - Tonic Receptors:
    - Adapt slowly to stimuli (e.g., pain).

Chemoreceptors:
- Respond to the presence of chemicals, critical for taste and smell functions.
Thermoreceptors:
- Detect changes in temperature.
Photoreceptors:
- Evaluate light presence: rods are sensitive to low light conditions, while cones facilitate color and detailed vision.
Mechanoreceptors:
- Sense touch, pressure, vibration, and stretch.
Nociceptors:
- Specialize in detecting pain stimuli.

Path of Light:
- Light travels through various eye structures in the following order:
- Cornea → Aqueous humor → Lens → Vitreous humor → Retina.
Pupil Regulation:
- The iris adjusts pupil size to control light entry.
Fovea Centralis:
- Designated area for the sharpest vision; conversely, the optic disc represents a blind spot in vision.
Aging Effect on Vision:
- Loss of lens elasticity leads to presbyopia, characterized by difficulty focusing on near objects.
Visual Pathway:
- Sequence as follows: optic nerve → optic chiasm → thalamus (lateral geniculate nucleus - LGN) → primary visual cortex.

Basic Tastes Identified:
- Five fundamental taste categories:
- Sweet, Sour, Salty, Bitter, Umami.
Flavor Dependence:
- Flavor perception relies on both tasting and olfactory inputs (smell).

Pathway Configuration:
- The olfactory pathway interacts with the hypothalamus and limbic system, which are integral to emotional responses associated with smells.

Sound Pathway:
- Sound travels through the ear in this sequence:
- Auricle → External acoustic meatus → Tympanic membrane → Ossicles → Oval window → Cochlea.
Function of Ossicles:
- Serve to amplify sound wave vibrations.
Hearing Process Sequence:
- Vibrations start at the tympanic membrane → ossicles vibrate → create pressure waves in the cochlea → hair cells then transduce these waves into nerve impulses.

Vestibular System Components:
- Semicircular canals detect rotational movements, while the utricle and saccule are essential for sensing linear acceleration.
Vertigo:
- Dysfunctions arising in the semicircular canals can lead to sensations of dizziness or vertigo.