Post-Synaptic Electrophysiology Quiz

Post-Synaptic Electrophysiology

• Ions move across the post-synaptic membrane due to neurotransmitter binding to receptor
• These cause an electrotonic potential (EP) in dendrites of the post-synaptic neuron
• The EP flows along the membrane surface to the axon hillock
• The EP from the dendrites is called a post-synaptic potential (PSP)

Post Synaptic Potentials

• Channels are proteins within dendrites
• Depend on the type of receptor/ion channel
• A Na+ channel allows Na+ to flow inward, causing a depolarizing or excitatory PSP (EPSP)
• A K+ channel allows K+ to flow outward, causing a hyperpolarizing or inhibitory PSP (IPSP)
• A Cl- channel allows Cl- to flow inward, causing a hyperpolarizing or inhibitory PSP (IPSP)

PSP's are Graded Potentials

• EPSPs and IPSPs are graded potentials (not all or none)
• Graded potentials depend on the amount of neurotransmitter released
• PSP size depends on the strength of stimulus

Postsynaptic Neurons Receive Many Inputs

• Up to 1,000 inputs onto postsynaptic neurons
• These inputs are synaptic connections

Summation of PSPs

• Summation can involve both EPSPs and IPSPs
• Occurs in time and space
• Summation is important for processing inputs, learning, and memory

Overview of Neuronal Signaling Physiology

• Presynaptic neuron releases neurotransmitters
• Postsynaptic neuron receives neurotransmitters
• Action potential occurs, causing synaptic transmission
• Neurotransmitter binding results in a EPSP or IPSP

Post Synaptic Regulation

• All neurons have the same basic electrophysiology
• Postsynaptic regulation differs due to multiple inputs, variety of neurotransmitters, different receptors, and intracellular pathways
• This allows the nervous system to coordinate virtually all cellular physiology

Summary

• Bioelectricity is the electrical activity in living organisms. It's a result of charged particles (ions) moving in and out of cells.
• Nervous systems are designed for optimum functioning.
• The diversity in nervous systems reflects differences in organsim lifestyle and habitat.

Functional Divisions

• Somatic: voluntary control
• Autonomic: involuntary control (sympathetic and parasympathetic)
  • Sympathetic: whole body, "fight or flight", organ-specific, "rest and digest"
  • Parasympathetic: organ specific, "rest and digest"

The Autonomic Nervous System (ANS)

• Most tissues are innervated by both sympathetic and parasympathetic divisions
• Two efferent neurons and peripheral ganglia are involved
• Integration occurs in ganglia

The ANS Divisions

• Sympathetic: more wide-spread (whole body effects)
• Parasympathetic: more organ-specific effects

Functions of the ANS

• Sympathetic: relaxes airways, increases heartbeat, inhibits digestion, and stimulates heart
• Parasympathetic: constricts airways, slows heartbeat, stimulates digestion, and inhibits heart.

Neurotransmitters & Receptors of The ANS

• Sympathetic: acetylcholine (preganglionic), norepinephrine/adrenoceptors (postganglionic)
• Parasympathetic: acetylcholine (preganglionic), acetylcholine/muscarinic receptors (postganglionic)

ANS Divisions Have Antagonistic Effects

• Sympathetic: more active when body energy stores need to be used ("fight or flight")
• Parasympathetic: more active when body energy stores are being conserved/restored ("rest and digest")

The ANS Activity

• Both divisions are always active, though one is typically more active
• Overall effect depends on which division is more active (sympathetic versus parasympathetic)

ANS Summary

• A major source of integration in the body
• Used to regulate and coordinate the majority of organ systems
• Extensive feedback loops maintain body homeostasis

Pressures on Nervous System Development

• Nervous systems in all animals are designed for optimum functioning.
• Nervous system organization in invertebrates and vertebrates reflects differences in lifestyle and habitat.
• Aquatic vs. terrestrial organisms present different pressures on the development of the nervous system.

Nervous System Evolution in Animals

• Evolution patterns demonstrate a diverse range of nervous system complexity from simple nerve nets in cnidarians to centralized brains in vertebrates.
• Key features like cephalization (concentration of ganglia in a head region) and the emergence of specialized structures (like brain and spinal cord) highlight evolution.

Nervous System Evolution in Chordates

• Brain regions are conserved and modified in different chordate lineages
• Selective pressure influences the relative size and complexity of brain regions to meet the environmental demands of different species.

The Mammalian Nervous System

• Mammalian nervous systems display extreme complexity.
• Brain regions show increasing folding, leading to increased surface area and more synaptic connections.
• This correlates with the more complex behavior/physiology of mammals.

Development of the Human Brain

• Embryonic period of the brain, different regions of the brain develop from different regions of the embryonic brain.
• Regions developed have specific functions in the adult brain.

An Example of Complexity

The mammalian nervous system is divided into functional regions.

Functional Divisions of the Vertebrate Nervous System

• Nervous systems of vertebrates have both central (CNS) and peripheral (PNS) systems
• Input to the CNS and output from the CNS are via afferent and efferent systems, respectively.
• Somatic and autonomic systems constitute the efferent system
• Somatic involves skeletal muscles.
• Autonomic involves smooth muscles, glands, and heart.