Anatomy and Physiology - The Somatic Nervous System

Flashcards generated from lecture notes on the Somatic and Autonomic Nervous Systems.

Sensory receptor/Primary neuron

Detects sensation from different sources and sends it to the CNS; converts the stimulus into an electrical signal.

Secondary Neuron

Occurs in the CNS, carries sensory information to the brain (thalamus).

Tertiary Neuron

Delivers the sensory signal to the cerebral cortex for processing.

Spinal Reflex

A reflex that is processed in the spinal cord.

Cranial Reflex

A reflex that is processed in the brainstem.

Intrinsic Reflex

A reflex that develops before birth.

Learned Reflex

A reflex that develops after birth.

Somatic Reflex

A reflex where the response is carried out by skeletal muscle.

Visceral Reflex

A reflex where the response is carried by smooth or cardiac muscle or a gland.

Ipsilateral Reflex

A reflex that begins and ends on the same side of the body.

Contralateral Reflex

A reflex that begins and ends on opposite sides of the body.

Withdrawal Reflex

A reflex where painful stimuli directly cause contraction of skeletal muscle to withdraw from the stimulus.

Stretch Reflex

Rapid, involuntary contraction of a muscle in response to being stretched to prevent overstretching.

Tendon Reflex

Inhibits muscle contraction to prevent overstretching of tendons.

Crossed-Extensor Reflex

Activates the opposite side of the body, usually in response to painful stimuli.

Sensory Receptors

Receive sensory information (like touch, temperature, or pain) and transduce it into electrical signals.

Adaptation

Allows receptors to become less sensitive to stimuli over time. Based on their rate of adaptation they can either be Phasic or Tonic receptors.

Phasic Receptors

Respond to a stimulus initially and then adapt quickly.

Tonic Receptors

Provide a constant response to a stimulus and adapt slowly or not at all.

Chemoreceptors

Detect changes in the concentration of specific chemical stimuli. Like flavors and smell

Osmoreceptors

Respond to solute concentrations of body fluids. Like dehydration, drinking water

Thermoreceptors

Detect temperature changes.

Mechanoreceptors

Detect physical stimuli like pressure and vibration.

Baroreceptors

Detect blood pressure changes. Like Standing up too fast - sends signals to the brain so you do not faint.

Nociceptors

Detect pain.

Photoreceptors

Detect light.

Exteroceptors

React to stimuli from the external environment.

Interoceptors

React to stimuli from internal organs and tissues.

Proprioceptors

Monitor the position and movement of body parts in space.

General Sense Receptors

Found all over the body.

Special Sense Receptors

Limited to the head and used for vision, taste, hearing, olfaction, and balance.

Unencapsulated Receptors

Dendrites extend into surrounding tissue to detect various stimuli.

Encapsulated Receptors

Dendrites wrapped in a capsule to enable function.

Free Nerve Endings

Detect pain and temperature. (Unencapsulated Receptor)

Merkel Cells

In the skin, used for discriminatory touch (shapes, edges, textures). (Unencapsulated Receptor)

Hair Follicle Receptors

In the skin, detect movement of hair. (Unencapsulated Receptor)

Tactile Corpuscles

In the dermis, detect light touch and low-frequency vibration. (Encapsulated Receptor)

Lamellated Corpuscles

In the dermis, detect deep pressure.

Bulbous Corpuscles

Detect stretching of the skin.

Receptive Field

The area from which a sensory receptor can detect stimuli.

Somatic Pain

Originates from skin, muscles, bones, and joints and visceral pain from internal organs, blood vessels, or the lining of a cavity.

Visceral Pain

Originates from internal organs, blood vessels, or the lining of a body cavity. Can share the same pathway are Somatic pain

Referred Pain

Occurs when the brain becomes confused as to the origin of the pain. Ex. Pancreatitis in back abdomen

Phantom Pain

Occurs when a limb is lost but the sensory nerves and pathways to the brain remain intact so the CNS continues to interpret signals

Cornea

Transparent front surface of the eye that helps focus light onto the retina.

Sclera

White, opaque part of the eye that provides protection and shape.

Retina

Converts light into neural signals sent to the brain.

Rods

Work in dim light and only detect white and black. Contain the pigment rhodopsin which allows you to see in low light.

What does the sympathetic division of the autonomic nervous system respond to?

Response to a threat to our homeostasis (stress) for enables survival. Increases oxygen, increase the sweating, brain becomes alert and your pupils dilate. Blood is shifted away from the digestive system and towards skeletal muscle.

What are the three neurons in the sympathetic pathways and what are their functions

Preganglionic neuron: first neuron, cell body is the thoracolumbar region

Ganglion : cluster of nerve cells where the signal is passed to the postganglionic neuron.

Postganglionic neuron : Second neuron cell body is in the ganglion. Receive signal from first neuron to tell Organ what to do.

Cones

Work in bright light and detect color.

Synopsis of the autonomic nervous system

Has two types of synopsis based on the type of neurotransmitter they use. cholingeric synapses and andergenic synapses

Cholinergic synapses (of the ANS)

Acetylcholine (ACh) is neurotransmitter released (sympathetic and parasympathetic)

Adrenergic synapses

Norepinephrine is neurotransmitter released (sympathetic)

Types of Cholinergic Receptors

Acetylcholine (ACh) is the neurotransmitter your body naturally produces.

• ACh can bind to two types of receptors:

• Nicotinic receptors

• Muscarinic receptors

Parasympathetic Division of the Autonomic

Nervous System

• Active when body is not stressed or under a threat

• Controls “rest and digest” activities

• Salivation

• Lacrimation

• Urination

• Digestion

• Defecation

• Sexual arousal

Autonomic Reflexes and Homeostasis

Pathways your body uses to respond to changes and maintain internal

homeostasis

• Important in maintaining parameters like:

• Blood pressure

• Heart rate

• Airway size (open or narrow)

• Digestive activity

Autonomic Plexuses

A plexus is a nerve network where sympathetic and parasympathetic axons mix. These plexuses help control automatic functions in different parts of the body. Each plexus targets specific organs:

Cardiac plexus → controls heart rate and contraction strength

• Pulmonary plexus → controls airway size in the lungs

• Esophageal plexus → controls swallowing and food movement

• Abdominal aortic plexus → controls the functions of abdominal and pelvic organs

• Inside the abdominal aortic plexus are sub-plexuses:

• Celiac plexus → liver, stomach, pancreas, etc.

• Superior mesenteric plexus → small intestine and the first part of the large intestine

• Inferior mesenteric plexus → later parts of the large intestine

• Hypogastric plexus → pelvic organs like bladder, uterus, rectum

Autonomic Tone= Balance control

Each organ is constantly influenced by either the sympathetic or parasympathetic system — even at rest — but one usually dominates depending on the organ.