A/P II Lecture Exam 2

What is a reflex response? List the two types?

Def: Involuntary motor responses to stimuli, that do NOT require “thinking” (i.e. more complex sensory integration in the cortex).

Types:

• Somatic - Skeletal Muscle

• Visceral - Visceral Organs

Reflexes are fast-acting and predictable, what does this mean.

Fast Acting: evolved for responses that require quick changes in phsyiology.

• Ex: Reduce Damage, Maintain Balance

Predictable: responses are stereotyped to repeat a required function.

What are the different types of somatic reflect responses?

Intrinsic v. Learned

What are the 5-steps of a general reflex arc?

1) Receptor - site of the stimulus action.

2) Sensory Neuron - transmits afferent impulses to the CNS.

3) Integration Center:

• Monosynaptic Reflex: sensory neuron synapses directly with motor neuron.

• Polysynaptic Reflex: interneurons are involved in the signal-relay circuit.

4) Motor Neuron: conducts efferent impulses to an effector muscle/organ.

5) Effector: muscle fiber or gland cell that responds to the efferent impulses by contracting or secreting.

Typically, what does the somatic division of the PNS control?

Voluntary Movement

Does the somatic division control some involuntary functions?

Yes

List some important involuntary reflexes controlled by the somatic division.

• Withdrawal Reflex - Pain Reflex

• Diaphragm/Intercostals - Contraction/relaxation of breathing skeletal muscles via phrenic nerve in (cervical plexus).

• Propioreceptor Reflexes - Sense stretch/pain in skeletal muscles to unconsciously control movements to prevent damage.

What are proprioceptors and where are they located? What do they monitor?

Located in skeletal muscles, within muscle spindles and golgi tendon organs; monitor stretch in skeletal muscles.

Briefly, how does the stretch reflex work, using muscle spindles? Why is it important?

Sensory neurons detect stretch, integrate information through either monosynapses (sesnroy neuron & motor neuron) or polysynapses (sensory, motor, & interneuron).

• Monosynapse - Stretched muscle contracts, resisting/reversing stretch.

• Polysynapse - Cause antagonistic muscle to contract.

Helps resist OVER-STRETCHING!

How does the tendon reflex work using the golgi tendon organ? Why is it important?

Sensory neurons detect contraction and integrate information via polysynapses (sensory, motor, & interneuron).

• Inhibitory synapse (-) causes contracted muscle to relax.

• Exciatory synapse (+) causes antagonistic muscle to contract.

Helps resist OVER-CONTRACTION!

Why are “involuntary” reflexes like the muscle spindle reflex not part of the ANS?

Because they wire to skeletal muscle and therefore part of the somatic division.

What responses does the autonomic nervous system (ANS) control?

Involuntary

What are the differences in targets between the somatic nervous system and the autonomic nervous system?

The SNS deals with conscious responses, producing (both voluntary and involuntary) somatic reflexes within skeletal muscles.

The ANS only deals with involuntary responses within smooth muscle, cardiac muscle, and glands.

What are the two divisions of the autonomic nervous system?

• Sympathetic Division (Fight or Flight)

• Parasympathetic Division (Rest & Digest)

Where do cell-bodies of motor-neurons in the parasympathetic division come from?

• Brainstem (Cranial Nerves)

• Spinal Cord

What are some key differences between the SNS and ANS?

• Circuit Architecture

  • SNS: ONE Step Relay (no synapses in PNS)

  • ANS: TWO Step Relay (synpases in PNS).

• Ganglia Position

  • SNS: NO Motor Ganglia

  • ANS: Motor Ganglia

• Myelination:

  • SNS: Heavy Myelination (Fast Signals)

  • ANS:

    • Preganglion Neurons - Light Myelination (Slow Signals)

    • Postganglion Neurons - Nonmyelinated (Slow Signals)

• Postganglion Neurotransmitters

  • SNS: Only Stimulates (+)

  • ANS: Stimulates/Inhibits (+/-)

• Synapses

  • SNS:

  • ANS: Involves the formation of variscosities to infiltrate different tissues, releasing LARGE amounts of chemical messengers (either neurotransmitters or hormones).

How many “steps” of motor neurons are there in PNS circuits of the somatic nervous system?

1

How many “steps” of motor-neurons are there in PNS circuits of ANS?

2

Are there motor ganglia in the somatic nervous system?

No

Are there motor ganglia in the ANS? Where are they located?

Yes, located in the PNS.

What are preganglionic neurons? Where are their cell bodies located?

Def: The first neurons in the ANS pathway that carry signals from the central nervous system (CNS) to autonomic ganglia, where they synapse with postganglionic neurons to form motor ganglia.

Locations:

• Sympathetic: Lateral Horn (T1-L2)

• Parasympathetic:

  • Brain Stem (Parasympathetic CN #3, 7, 9. & 10)

  • Sacral Spinal Cord (S2-S4)

What are postganglionic neurons? Where are their cell bodies located?

Def: The second neurons in the ANS pathway, responsible for carrying signals from the autonomic motor ganglia to the target organs (i.e smooth muscles, cardiac muscle, & glands).

Locations:

• Sympathetic: Sympathetic Chain/Prevertebral Ganglia

• Parasympathetic: Near/Within Target Organs

Which ANS division has cell bodies in the lateral gray horn of the spinal cord?

Sympathetic

Where do cell-bodies of motor-neurons in the sympathetic division come from?

Lateral Horn/Thoracolumbar (T1-L2)

Where do ganglia of motor-neurons (motor ganglia) in the sympathetic division typically reside?

Sympathetic Trunk

What are sympathetic trunk/chain ganglia? Where are they located?

A pattern that ganglia near the spinal cord assume/take on as a result of interlinking fibers.

How long are preganglionic and postganglionic neuron in the sympathetic division?

Preganglionic Neurons: Short

Postganglionic Neurons: Long

Where do cell bodies of motor-neurons (motor ganglia) in the parasympathetic division typically reside?

Craniosacral (Autonomic CN & S2-S4)

Where do ganglia of motor neurons in the parasympathetic division typically reside?

Far from Spinal Cord; Close to Target Organs

How long are preganglionic and postganglionic neuron in the parasympathetic division?

Preganglionic Neurons: Long

Postganglionic Neurons: Short

Approximately how much of the parasympathetic division does CNX supply?

90%

What are the myelination patterns of neurons in the SNS and ANS?

• SNS: Heavy Myelination (Fast Signals)

• ANS:

  • Preganglion Neurons - Light Myelination (Slow Signals)

  • Postganglion Neurons - Nonmyelinated (Slow Signals)

Can motor-neurons in the SNS stimulate and inhibit?

Just Stimulate (+)

*Release ACh to stimulate muscle contractions.

Can motor-neurons in the ANS stimulate and inhibit?

Yes, can stimulate (+) and inhibit (-).

*Release ACh or norepineephrine which can have either effect (+/-) depending on the target.

Where is acetylcholine (ACh) used in the SNS and the ANS?

• SNS: Released after motor neurons wire to skeletal muscles to stimulate muscles, causing them to contract.

• ANS: Used by ALL preganglionic divisions to stimulate the next neuron at the synapse (i. postganglionic cell).

Define: Cholinergic Receptor

List the subtypes.

Def: Protein receptors that bind to ACh.

Types:

• Nicotinic

• Muscarinic

Define: Nicototinic

A neurotransmitter that stems from cholinergic receptors and is always stimulatory.

Locations:

• Dendrites of Postganglionic Cells

• Skeletal Muscle Sarcolemma

• Adrenal Medulla

Define: Muscarinic

A neurotransmitter that stems from cholinergic receptors and is either stimulatory or inhibitory, depending on the sub-class of receptor in the target.

Locations

• ALL Parasympathetic Targets

Where is ACh stimulatory? What cholinergic receptors mediate stimulatory responses?

ACh is stimulatory in areas like muscle contraction (via nicotinic receptors) and certain smooth muscle and glandular responses (via muscarinic receptors), with the precise response depending on the receptor type and location.

Where is ACh inhibitory? What cholinergic receptors can mediate inhibitory responses?

ACh is inhibitory primarily when it binds to muscarinic receptors, such as M2 receptors (inhibiting/decreasing heart rate) and M4 receptors (inhibiting neurotransmitter release in the CNS).

Where is norepinephrine/epinephrine (NE/E) used in the SNS and ANS?

• SNS: NOT USED (only rely on ACh)!

• ANS: Mainly used in Sympathetic Division

  • Secreted: Postganglionic Sympathetic Cells/Neurons

  • Secreted: Chromaffin Cells of Adrenal Medulla

Define: Adrenergic Receptor

A neurotransmitter that is either stimulatory or inhibitory, depending on the type of receptor in the target.

What are alpha and beta receptors?

Alpha and beta receptors mediate a wide range of physiological effects in response to norepinephrine (NE) and epinephrine (E). Alpha receptors generally produce stimulatory effects (like vasoconstriction via α₁ and feedback inhibition via α₂), while beta receptors mediate stimulatory effects such as increasing heart rate (β₁) or relaxing smooth muscles (β₂). The specific effects depend on the receptor subtype and location in the body.

Where is NE stimulatory? What adrenergic receptors mediate stimulatory responses?

Norepinephrine (NE) is primarily stimulatory in the body, increasing heart rate, blood pressure, energy production, and facilitating the body’s response to stress or physical activity. It acts through alpha and beta adrenergic receptors to produce these effects.

Where is NE inhibitory? What adrenergic receptors can mediate inhibitory responses?

NE's inhibitory effects are primarily mediated through α₂ receptors, which help regulate the release of NE and balance sympathetic nervous system activity. In some cases, β₂ receptors may also be involved in inhibitory responses, especially in smooth muscle relaxation.

Understand how a single hormone, like NE in the sympathetic division, can mediate many different responses across different tissues.

Different Receptors

What is the sympathetic nervous division? What are its responsibilities?

• Fight or Flight

• Responsibilities:

  • Mobilizies during activity, stress or emergency situations.

  • Triggers changes needed for rapid response and decreases nonessential processes.

What is the parasympathetic nervous division? What are its responsibilities?

• Rest & Digest

• Responsibilities:

  • Conserves Energy

  • Directs Housekeeping Activities (i.e Digestion, Urination, Defecation, Heart System, Breathing System, etc)

Explain dual innervation and why is it important for the ANS.

Def: When both autonomic divisions wire to the same targets and utilize their opposing stimulatory (+) and inhibitory (-) functions in order to maintain homeostasis.

What are variscocities? How are the different than neuron-neuron synapses?

Def: Swellings along autonomic postganglionic neuron axon terminals that release chemicals that infiltare different tissues to release LARGE amounts of chemical messengers (either neurotransmitters or hormones).

Different that neuron-neuron synapses because they diffuse chemical messengers over larger areas, leading to more widespread effects.

What is the distinction between a hormone and a neurotransmitter? How are they different, concerning where they migrate?

Neurotransmitters and hormones are both chemical messengers, however they migrate to distinct locations:

Neurotransmitters remain in the synapse region (synaptic cleft); hormones are released into the bloodstream.

What is the endocrine system? How does it differ from the nervous system?

Nervous System

• Mode of Communication: Neurons & Neurotransmitters

• Speed of Response: Fast Electrical Impulses

  • Needed due to changing environment (SNS & ANS).

• Duration of Effects: Short-Term

• Target Areas: Specific, Localized Areas

Endocrine System

• Mode of Communication: Hormones

• Speed of Response: Slow

• Duration of Effects: Long-Term

  • Regulate growth, development, behavior, reproduction, metabolism, & immunity.

• Target Areas: Varied Long-Distance Cells/Organs

What is a gland? What types of glands are in the endocrine system?

Def: A group of cells that secrete one or more products.

Types:

• Exocrine Glands - secretions exit via DUCTS.

• Endocrine Glands - secretions (hormones) released into interstitial fluid and bloodstream (NO DUCTS).

What brain region provides a link to the ANS and the endocrine system?

Hypothalamus

*Recieves sensory information to regulate many ANS processes.

What is hypothalamus’ glandular connection to the endocrine system?

Endocrine signals (via hormone release through the pituitary gland)

List examples of endocrine glands:

• Pituitary Gland

• Thyroid Gland

• Parathyroid Gland

• Adrenal; Gland

• Pineal Glands

List the organ(s) that stem from the neuroendocrine organ. Function?

Organ: Hypothalamus

Function: Neural & Hormone Function

List examples of endocrine organs (non-neuroendocrine organs).

Several organs have subdivisions of secretory endocrine cells:

• Pancreas

• Gonads

• Placenta

Define: Hormone/Signaling Molecule

Chemical messengers secreted into the bloodstream or into interstitial fluid to communicate signals to organ systems.

Tendon to reach all parts of the body, but only target cells respond due to specificity of receptors.

At the molecular level, how do receptors work to detect/bind chemical messengers?

Signaling molecules have target cells that receptors detect/bind to as a result of compatible 3D shapes (Hint: Lock & Key).

What are the main types of hormones in the endocrine system?

1) Steroids (Long-Range, Modified Lipids)

2) Amino Acid Based

3) Eicosanoids

What are the properties of these different signaling molecules? List some examples.

Steroids

• Derived from Cholesterol (Lipids)

• Most steroid hormones originate from the Gonads or Adrenal Gland

• Lipid-Soluble; Hydrophobic

Amino-Acid Based

• Most common in body.

• Some Hydrophilic; Some Hydrophobic

• Range in size, but all include some form of modified amino acids or peptides.

Eicosanoids

• Short Range

• Lipid Based

Know the difference between endocrine, paracrine, and autocrine chemical messengers.

Endocrine Chemical Messengers: secreted via ductless glands, reach target cells by entering circulatory systems (bloodstream or Lymphatic System), & have long-acting broad effects.

Paracrine Chemical Messenger: secreted in response to local stimuli and act on neighbor cells via diffusion to produce rapid responses within tissues.

Autocrine Chemical Messenger: produced by a cell and are “self-governed” by receptors on the cell’s own membrane (secreting cells are themselves the target).

• Often in POSITIVE FEEDBACK to AMPLIFY responses.

What type of feedback loop are typically involved in autocrine responses?

Positive Feedback (Amplify Responses)

What are neurohormones?

Special Brain or ANS neurons that release neurotransmitters that become hormones because they enter/travel in the bloodstream.

What are pheromones? Do humans use a lot of pheromones?

Def: Hormones secreted from glands that act OUTSIDE of the body.

• Produced by one individual in order to change the behavior and physiology of other individuals:

  • Species Recognition

  • Social Interaction & Reproduction

  • Navigation & Territory Marking

While humans do produce pheromones, their role in human behavior is less pronounced and not as well understood as in other species.

Know the differences between Water-Soluble and Lipid-Soluble Hormones, in regard to:

• Release from Secretory Cells

• Migration through bloodstream, interstitial fluid, or lymphatic vessels.

• Receptor-Binding at the Target Cells

• Induction of Response in the Target Cells

What is an example of a water-soluble hormone? What is a second messenger?

• Ex: Epinephrine

• Secondary Messenger: a molecule that signals water soluble hormones to cross cell membranes.

What is an example of a lipid-soluble hormone? What is a transcription factor?

• Ex: Cortisol

• Transcription Factor: hormones that directly enter NUCLEUS, inducing changes in gene expression.

Why don’t all cells respond to all hormones, and in the same way?

Not all cells express the same receptors nor do all cell types respond in the same way.

What is homeostasis? What brain region controls many homeostasis processes?

Def: Maintaing a stable internal environment despite fluctuating external conditions.

• Homeostatic Control Center: Hypothalamus

How does the hypothalamus work like a thermostat during thermoregulation?

Fluctuations above/below biological set points serve as stimuli, which are detected by sensors, triggering responses (release of hormones) that return the condition back to the set point.

What is a negative feedback loop? How does it work, generally?

Hormones released from endocrine

cells travel through the bloodstream, and

interact with the receptor of a target

cell to cause a response. Eventually, a negative feedack loop inhibits a response by reducing the

initial stimulus.

What are some biological examples of negative feedback loops?

• Body Temperature/Thermoregulation

• Blood Glucose Level Regulation

What process do insulin and glucagon control, via negative feedback loops?

Antagonist hormones that maintain glucose homeostasis.

What is a positive feedback loop? How does it work, generally?

An external stimulus triggers a response that AMPLIFIES that same response; moving away from the set point.

What are some biological examples of positive feedback loops?

• Childbirth Contractions

• Blood Clotting

• Lactation

What must every positive feedback loop have to stop pathological conditions?

A “circuit breaker” from an outside pathway.

What are the different ways glands in the endocrine system can be stimulated to secrete?

• Humoural Stimulus

• Neural Stimulus

• Hormonal Stimulus

What is a tropic hormone?

A hormone that acts indirectly by stimulating other endocrine glands.

What is a non-tropic hormone?

A hormone that acts directly by stimulating responses in non-endocrine glands.

What is the pituitary gland? What cells make up each half of the pituitary gland?

• Aka: Master Endocrine Gland

• Cells:

  • Anterior Pituitary Gland - Endocrine Cells

  • Posterior Pituitary Gland - Neural Tissue

Remember: Anterior Pituitary Gland respond to hypothalamus by producing and secreting hormones (true endocrine gland); Posterior Pituitary Gland ONLY stores hormones already made form hypothalamus (false endocrine gland).

What hormones are secreted by the anterior pituitary?

• FSH

• FLH

• ATCH

• TSH

• PRL

• GH

What hormones are secreted by the posterior pituitary?

• Antidiuretic Hormone (ADH)

• Oxytocin

Briefly, what are the functions of hormones from the posterior pituitary?

• Antidiuretic Hormone: Water Retention

• Oxytocin:

  • Childbirth Contractions

  • Breastmilk Ejection

Is oxytocin topic or non-tropic?

Non-Tropic

Is growth hormone tropic or non-tropic?

Both

What are the short-term responses of growth hormone?

• Tissues

• Cells

What are the short-term targets of growth hormone?

• Raised Blood Glucose Levels

• Increased Metabolism

What are the long-term responses of growth hormone?

Stimulated Growth Functions:

• Nutrient Uptake for DNA Replication

• Cell Division

• Formation of Collagen & Bone Matrix

What are the long-term targets of growth hormone?

• Bone

• Skeletal Muscle

Does GH generally act “directly” or “indirectly” in short-term responses?

Directly

Does GH generally act “directly” or “indirectly” in long-term responses?

Indirectly

How is GH controlled? What is somatostatin (GHIH)?

• Controlled via negative feedback loops.

• GHIH is a hormone that inhibits the release/production of Growth Hormone Reelase Hormone from the hypothalamus.

What are some consequences of improperly regulated GH?

• Too Little: Dwarfism

• Too Much: Gigantism

What does recent research say about how hot flashes are generated during menopause?

Hot flashes during menopause are likely due to LOW ESTROGEN LEVELS causing RAPID STRESS RESPONSES.

What stimulates short-term vs. long-term stress responses?

Sympathetic vs. Pituitary, respectively.

Do short-term and long-term stress responses both (eventually) use elements of the

Endocrine System?

Yes

What are some motor-responses triggered by short-term stress response?

• Increased Heart Rate

• Increased BP

• Increased Blood Glucose Levels

• Bronchiole Dilation

• Changes in blood flow leading to increased alertness and decreased digestive & renal activity.

• Increased Metabolic Rate