Chedrese– Week 1 to 5 Flashcards
Metazoa includes all organisms in the animal kingdom; break this down into two subkingdoms and explain their differences.
Parazoa: (sponges) A primitive subkingdom that includes the sponges (phylum porifera), considered by many zoologists to be intermediate between the subkingdoms protozoa and metazoa.
Eumetazoa: A subkingdom comprising all multicellular animals with differentiated tissues.
What is a Protista? What is their significance in studying evolution?
A group of unicellular and multicellular eukaryotes that may have features of both animals and plants
It is believed to likely be the ancestor of the animal kingdom.
Unicellular protists with more animal-like characteristics can be referred to as ______, though this term is increasingly incommon.
Protozoa
What protozoan-like colonial flagellated species can be attributed as the first evolutionary evidence of intercellular communication (aka the closest living relatives of modern animals)?
Choanoflagellates
What are sponges?
Sessile, aquatic animals (and the closest relative of the choanoflagellates) of the subkingdom/suborder parazoa and phylum Porifera.
How do sponges consume nutrients?
Sponges feed through phagocytosis of individual cells (called filter feeding)
How do sponges communicate?
Through chemical signals that cause the shrinking and expanding of the cells (similar to muscle contractions).
No nervous system but, proteins are involved in electrical signal reception.
Tissue stability is achieved through cell junctions and the extracellular matrix. This was a crucial step in the transition to multicellularity. Describe these (3) cell junctions.
(1) Tight junctions (or zona occludens): rows of transmembrane proteins that bind to the corresponding membrane proteins of the adjacent cell.
(2) Gap (nexus) junctions: intercellular channels that directly communicate the cytoplasm of two cells, allowing passage of ions and small molecules (cytoplasmic streaming)
(3) Anchoring junctions: link the cytoskeleton with the extracellular matrix
- Adherens junctions, hemidesmosomes, and desmosomes
- joins cells through cedherins of the same tissue by homophilic binding attached to intermediate filaments of the cytoskeleton
What allows cells to recognize and bind to one another?
A common proteome of identical proteins
What are the (2) hallmarks of multicellularity?
(1) the formation of space between cells known as the interstitial space (IS); filled with interstitial fluid (IF) that bathes and surrounds the cell
(2) controlling of internal media; including nutrients, pH, temperature, and electrolytes
Describe the flow of sodium and potassium through animal body fluids and tissue compartments.
Intracellular (ICF): low Na+ and high K+
Extracellular (ECF): high Na+ and low K+
- Interstitial fluid
- Intravascular: plasma is the ECF of blood
- Transcellular fluid: cerebrospinal, synovial, ocular, peritoneal, and pericardinal fluids
https://youtu.be/_bPFKDdWlCg
Describe the Extracellular Matrix (ECM).
A network of proteins, glycoproteins, glycosaminoglycans, and collagen that surround, support. and give structure to cells and tissues
- produced by sponges and other primitive organisms
- main structural protein in the interstitial space
- mostly found in fibrous tissues
How are the cuticles of worms and insects and the shells of mulluscs formed?
Sheet-like depositions of ECM form the basement membranes on which various epithelial cells rest
True or false? Nearly all animals undergo some form of sexual reproduction.
True; some animals can reproduce asexually but it is uncommon
Fertilization is the fusion of sperm and egg to produce a new organism. Describe the process in detail.
Shortly after penetration the sperm nuclear membrane fuses with the nucleus of the egg resulting in a diploid cell (zygote) which divides rapidly into half-sized daughter cells of the same size as the zygote (blastomeres) then develops into a morula.
Define zygote.
a diploid cell resulting of fertilization
Define blastomeres.
daughter cells of the dividing zygote
What is a morula?
a compact mass of cells derived from the blastomeres (or daughter cells of the zygote)
What form follows fertilization and the morula?
Morula derives into a hollow sphere of single layer of cells called the blastula
What are the two main events that occur at the stage of morula?
(1) Compaction
(2) Expression of the Na+/K+ -ATPase (high concentration solute draws in water)
Describe the process of blastulation of the embryo/blastula.
Hint: hemispheres
During blastulation the embryo is divided into two hemispheres:
(1) The animal pole that consists of small blastomeres that divide rapidly and differentiate into the later embryo itself, forming the three primary germ layers
(2) The vegetal pole contains large yolky cells that divide very slowly and differentiate into the extra-embryonic membranes that protect and nourish the developing embryo (ex placenta in humans or chorion in birds)
Compare Protostomia and Deuterostomia.
Protostomia is the clade of animals that during embryonic development form the mouth before the anus.
Deuterostomia is the clade of animals during embryonic development form the anus before the mouth.
What cleavage do Protostomia exhibit and what are some organisms that establish this way?
Spiral cleavage: newly produced cells lie in the space between the cells immediately below them. The development path of each cells is determined as they are produced.
Ex) Arthropods, molluscs, annelids, flatworms, and nematodes
What cleavage do Deuterostomia exhibit and what are some organisms that establish this way?
Radial cleavage: newly produced cells lie directly above and below other cells of the embryo. Development fates of the first few cells are not determined and a cell removed from the morula will go on to form a complete organisms (identical twins).
Ex) vertebrates, including humans and echinoderms (sea stars)
What is the Inner cell mass (ICM) of deuterostomes?
Embryoblasts: pluripotent cells from the blastula that will eventually give rise to the definitive structures of the fetus. They are formed in the earliest steps of development before implantation and lies within the blastocyst cavity, surrounded by the trophoblast.
What is the Gastrula and how is it formed?
The structure of cell differentiation composed of the ectoderm, mesoderm, and endoderm. The blastula invaginates and further differentiates into these three germ layers.
The ectoderm, mesoderm, and endoderm give rise to what bodily structures?
Ectoderm: skin and nervous system
Mesoderm: muscles and skeleton
Endoderm: digestive tract
Describe the Primitive Streak.
A midline strip that forms on the dorsal face of the blastula. Through this midline, bilateral symmetry is established, creating the left-right cranial-caudal body axes.
It also marks the beginning of gastrulation and initiates germ layer formation.
Describe the location, structure, and function of the Coelom.
The coelom is the fluid-filled body cavity located between the intestinal canal and body wall, surrounding and containing the internal organs.
During gastrulation, two layered membrane derived from the mesoderm creates a lining that covers and protects most internal organs (termed mesothelium).
A blind pouch called the archenteron forms in early development of the digestive tube.
Mesenchyme tissue gives rise to which cell layer? Describe it’s structure and purpose.
Mesenchyme is a tissue that gives rise to the mesoderm. It is comprised of loose cells embedded in a mesh of proteins and fluid, called the extracellular matrix that is formed when the archenteron touches the interior wall fo the blastocoel.
It will directly give rise to most of the body’s connective tissues (bones, cartilage, lymphatic and circulatory systems).
The interactions between _________ and _________ contribute to form nearly every organ in the body.
mesenchyme and epithelium
Compare the blastopore and archenteron.
The blastopore is the opening of the invagination and the archenteron is the structure/substance of the inner body cavity (coleum).
The development of the mesoderm induces the growth of what other structures?
The neural plate, precursor to the nervous system, the notochord, and [missed]
What is a notochord?
A flexible rodlike structure that serves as a primary longitudinal structural element of the phylum cordate (spinal cord)
Animals have three primary embryonic cell layers. What are they and how do they arise?
Ectoderm, mesoderm, and endoderm
PGCs arise from a population of pluripotent cells in the ectoderm.
In a simple organisms the gastrula has only an ectoderm and endoderm. What are these species with only two germ layers called? Give two examples.
Diploblasts; Cnidaria and Ctenophora (jellyfish, corals, hydra)
What are the first 5 stages in Triploblastic organism development?
(1) Fertilization
(2) Cleavage
(3) Gastrulation
(4) Organogenesis
(5) Neurulation
What is organogenesis and terminal differentiation?
The growth of more and/or larger cells along with the differentiation of cells and, eventually, the production of organs in living organisms.
Organogenesis is the phase of embryonic development that starts at the end of gastrulation and continues until birth
What is the notochord, its origin, and purpose?
a cartilaginous skeletal rod supporting the body in all embryonic and some adult chordate animals.
Mesodermal rod-shaped structure formed during gastrulation from cells migrating from the primitive streak.
Provides rigidity along the dorsal or posterior side of the embryo, forming the central axis of the animal body.
The notochord defines a specific phylum. Which is it? How does the notochord structure differ in fishes and amphibians specifically?
Chordata;
persists in the trunk and tail of fishes and amphibians
How does the notochord provide body support?
Contains the nerve cord which is the main communication stem of the nervous system.
The gastrointestinal tract is below.
During development, what structure replaces the notochord?
Hollow interlocking vertebra and cartilaginous substances between vertebrae called intervertebral discs
What is the initial major event of organogenesis?
Neurulation
What is neurulation and describe the development process.
The transformation of the neural plate into a neural tube,
starting with a thickening of the ectoderm located along the dorsal midline of the embryo, giving rise to the neural tube, neural crest, and dual sides of epidermis.
After the stage of neurulation, what is the embryo called?
neurula
Describe neural tube formation.
The neural plate folds into the neural tube and differentiates into the peripheral and enteric neurons, and glial cells of the nervous system, which will eventually cause the differentiation of the spinal cord and brain (forming the central nervous system).
During neurulation, the body develops into segments with specialized functions. What are these segments called and describe their structure.
Termed somite or primitive segments.
A set of bilaterally paired blocks of mesoderm that form along the head-to-tail axis
(will give rise to the cells of vertebrae and ribs, and define it as repeated structures)
What are ganglia and their function?
Clusters of nerve cell bodies and function like relay stations with chemical messages
What is the ocelli and how is it unique in jellyfish?
Ganglia evolved into a primitive eye;
In jellyfish ganglia functions as a pacemaker and also evolved into statocysts (fluid-filled sacs with solid particles termed statolith)
Describe neurogenic signalling or contraction.
contraction of the heart or heart-like muscles through electrogenic stimulation
Describe the nervous systems of Echinoderms.
Echinoderms (starfish; radially symmetric marine animals) do not have a true central nervous system, but instead have ocelli that detects pigments that stimulate the centralized formation of ganglia
In what organisms did a true central nervous system first evolve?
A true CNS first evolved with bilateral symmetry in segmented animals (arthropods, annelids, chordates)
What is cephalization?
An evolutionary trend in which the mouth and sense organs become concentrated at the front end of an animal.
What are the advantages of cephalization?
Sensory information about the environment is initially detected in the anterior region:
Detect images, developed learning abilities, and memory and ultimately self-awareness
The most advanced invertebrate brains are found in which organisms?
cephalopod mollusks (squid, octopi, cuttlefish, etc)
Define vertebrates.
Comprise all animals with an internal skeleton
All vertebrates are built along the basic chordate body plan that comprise:
- the skull
- a vertebral column
- the spinal cord
- ganglia
- nerves
The central nervous system (CNS) is divided into what two major parts?
the brain and the spinal cord
The brain lies within the skull and consists of four principle parts:
(1) Brain stem
- midbrain
- pons
- Medulla oblongata
(2) Cerebrum
(3) Cerebellum
(4) Diencephalon
- thalamus and hypothalamus
The Hypothalamus derives from which part of the brain? Where is it located?
Derives from the diencephalon
Located below the thalamus, extend to the pituitary gland
Describe the structure of the vertebral column and the spinal cord.
The vertebral column (spinal column or spine) is a long tube-like structure composed of a series of bone segments termed vertebrae (31 in humans) that extends from the skull to the coccyx.
The spinal cord is a long, thin structure made up of nervous tissue that extends from the medulla oblongata to the lumbar region of the vertebral column. It encloses a central canal that contains cerebrospinal fluid and a pair of spinal nerves come out of each segment with motor and sensory nerves.
What is cerebrospinal fluid (CSF)?
The CSF is a clear, colourless body fluid found in the brain and spinal cord that is produced by glial cells in the brain.
What is the blood-brain barrier (BBB) and its purpose?
The BBB is a highly sensitive semipermeable border of endothelial cells rich in tight junctions that separates the brains extracellular fluid (cerebrospinal fluid) and circulating blood. It’s main purpose is to restrict the diffusion of microscopic materials in and out of the brain to allow the transport of nutrients but prevent harmful materials invading.
What is the skull and its latin name?
Cranium
A bony structure that forms the head in vertebrates
Do insects and invertebrates have skulls?
no.
The nervous system is composed of two types of cells. What are they and their functions?
neural and non-neural cells;
Neurons: highly specialized cells that can generate and transmit information in the form of electrical signals; composed of three main parts: the cell body, the axon, and the dendrites.
Glial cells: commonly known as the glue of the NS; together with the capillaries and neurons form a grey-brown coloured tissue called grey matter. Glial cells and capillaries maintain stability of the
NS tissue, provide support and protection to the neurons and play a role in neurotransmission.
What are the three types of neurons?
motor, sensory, and Purkinje (also known as central neurons)
What are the nodes of Ranvier?
Periodic gap in the myelin insulation sheath with large amounts of ion channels that facilitate rapid movement of Na+/K+ and conduction of nerve impulses.
- uninsulated gap of ~1 micron formed between the myelin
sheaths.
Define nerves.
Enclosed cable-like bundles of axons surrounded by three layers of connective tissue
How are nerves classified?
(1) According to the directions of the transmitted impulses:
- Afferent, efferent, or mixed
and
(2) Based on where they connect to the CNS
- Spinal nerves or cranial nerves
What are Ganglia (or a ganglion) and its function?
Ovoid structures containing clusters of neuron bodies with localized interconnections and glial cells. Function like a relay station: one nerve enters to the ganglia while other nerves exit.
Where are the ganglia located in vertebrates?
Located along the spinal cord at the dorsal and ventral roots of the spinal nerve
There are 31 pairs of spinal nerves along the human vertebral column that are organized into plexus. What are they?
Cervical, Thoracic, Lumbar, Sacral, and coccygeal
What are cranial nerves?
Nerves that are present on both sides of the body and emerge directly from the brainstem in pairs. There are intracranial paths within the skull and extracranial emerge through holes in the skull called foramina. These nerves are numbered with roman numerals.
What is the 10th cranial nerve and why is it important?
the Vagus nerve is found in many parts of the body
________ pituitary is mainly nerve tissue and _______ pituitary is mainly glandular (hormonal) tissue.
posterior; anterior
Communication in the animal body has three main components:
(1) Chemical and electrical signals
(2) A system of signal reception (ion channels and cell receptors)
(3) A cellular response (opening ion channels, internal response pathways)
Molecules secreted into the body fluids binds to what protein receptors?
ligands
What are endocrine glands?
organs that produce and secrete chemical signals (termed hormones)
What are neurons?
functional units of the nervous system; produce neurotransmitters and generates electrical signals in the form of action potentials (rapid changes in the polarity of the membrane that moves unidirectionally)
What are hormones?
signalling molecules synthesized and secreted by specialized cells that are released into the extracellular space and exert specific biochemical actions on target cells located at distant sites
What are neurotransmitters?
signalling molecules synthesized and secreted by neurons that are released into the space of a synapse and exert specific biochemical actions on a postsynaptic cell
The neurotransmitters termed monomines are derived from…
amino acids
The neurotransmitter Acetylcholine is derived from…
acetyl-CoA
What are two membrane-soluble chemical signals?
Thyroid hormones and aldosterone
What is homeostasis?
The tendency to maintain a stable, relative constant internal environment
What are the 6 physical and chemical variables of homeostasis?
(1) Human body temperature: 37°C
(2) Blood pressure: 120/80 mm Hg
(3) Heart rate: 60 to 100 beats/minute
(4) pH of the extracellular fluids: 7. 365
(5) Blood glucose: 5 mmol/L
(6) Concentration of electrolytes: Na+, Cl-, and organic solutes in the ECF
What two organs that maintain homeostasis?
The hypothalamus and the pituitary gland
What is feedback regulation? What are two mechanisms of control?
Environmental influences on body variables
Mechanisms of control: Negative and positive feedback regulation
What are at four interdependent components for a regulated variable in the negative feedback cycle (ex: the temperature regulatory system)?
(1) set point
(2) sensor
(3) integrator
(4) effector
In the regulation of body temperature, what is activated by the cold?
Shivering, hunger, increased voluntary activity, increased secretion catecholamines, decreased heat loss, cutaneous vasoconstriction, curling up, and horripilation
In the regulation of body temperature, what is activated by the heat?
Increased heat loss, cutaneous vasodilation, sweating, increased respiration, decreased heat production, anorexia, apathy and inertia
Give two examples of positive feedback cycles.
Hormonal and neural regulation of glycemia & childbirth/breastfeeding
What are endocrine glands?
Organs that produce and secrete chemical signals termed hormones into the ECF then general circulation
What are exocrine glands? Give a few examples.
organs that release their product through a duct or opening of the body;
sweat glands, lacrimal, salivary, mammary, and digestive glands in the stomach, pancreas, and intestines
they produce sweat, tears, saliva, milk, and digestive juices that are released through ducts
Name the principles of electrical signalling in the nervous system.
(1) All animal cells are surrounded by a membrane
(2) the plasma membrane is an insulator
(3) the plasma membrane serves as a diffusion barrier
(4) the plasma membrane has ion channels imbedded
Why is the giant squid used for its axons as a research model?
Very large and thick axons; unmyelinated
At rest, what is the differences in charges between the interior and exterior of the membrane?
ranges from -40mV to -80mV
What are three main components that contribute to membrane polarization?
(1) Na+/K+ -ATPase pump
(2) ion channels
(3) large negatively charged proteins
If the membrane is like a battery, how is it recharged?
The Na+/K+ -ATPase pump transports 3 Na+ out for every 2 K+ moved into the cell
What are Na+/K+ concentrations, relatively, at rest and what is the concentration gradient?
There are more Na+ outside of the cell and more K+ inside of the cell;
Thus, Na+/K+ -ATPase creates a concentration gradient of:
Na+ to move into the cell and K+ to move out of the cell
Ion channels (ATP-dependent ion pump) creates a ________ intramembrane environment, and a concentration gradient, or electrical force, on ______ side(s) of the membrane.
negative; both
Large and negatively charged proteins (anions) are more abundant…
inside of the cell (because they are too large to leave); creating a intercellular negative environment
What are the two basic roles of the membrane potential?
(1) Works like a battery, as it is a reservoir of energy
(2) Can respond to stimulus with swift changes in potential, through electrical signals in the form of action potentials
Describe the role of the voltage-gated Na+ channels in depolarization.
Hint: briefly describe how the channel functions
(1) Closed at the resting potential, the channel is closed
(2) Open in response to a nerve impulse, the gate opens and Na+ enters the cell
(3) Inactivated for a brief period following activation, the channel does not open in response to a new signal
Describe the role of the voltage-gated K+ channels in depolarization.
Hint: voltage-gated K+ channels also termed leaking channels
At rest, the membrane is more permeable to potassium than to sodium.
Potassium tends to easily leak out of the cell
Describe the ion channels at resting potential.
- K+ and Na+ leak channels are open
- Na+/K+ pumps 3 Na+ out and 2 K+ in
- K+ and Na+ voltage-gated channels closed
A weak stimulatory/inhibitory signal causes what graded potentials?
Hint: answer for each situation
A weak stimulatory signal causes graded depolarization.
A weak inhibitory signal causes graded hyperpolarization.
What fashion does the membrane polarize in, when the intensity of the stimulus overcomes a threshold?
all or none fashion; depolarization reaches a peak and never goes above the peak regardless of the intensity of the stimulus
Summarize the Action Potential Cycle in neurons.
(1) The membrane is at rest; so the sodium channel is closed but active and the potassium channel is closed
(2) the sodium channel opens when stimulus reaches the threshold. Membrane depolarizes above the threshold and action potential begins
(3) the sodium channel remains open during the raising phase of depolarization and sodium rushes into the cell
(4) Sodium channel inactivates and potassium channel opens one msec after the start of depolarization
(5) repolarization starts when intracellular potassium falls
(6) at the end of repolarization the sodium channel closes but becomes active. A new stimulus can open the sodium channel before completion of the cycle
(7) Potassium channel during hyperpolarization; the leaking of K+ channel is responsible for the electronegativity of the membrane during hyperpolarization as potassium flows out of the cell
(8) Potassium channel closes and neuron is back into the resting potential
Compare absolute and relative refractory periods.
Absolute refractory period of a neuron is the period of time during which no amount of external stimulus will generate an action potential. Relative refractory period is the period of time during which only a large stimulus will generate an action potential.
What are the two physiological refractory period connotations?
Sub-threshold stimulus: small or short stimulus that does not reach action potential
Supra-threshold stimulus: long and/or large stimulus that reaches action potential
Describe the signal directionality (or the direction of travel of action potential).
(1) In response to a signal, the soma end (bigger one) of the axon becomes depolarized
(2) The depolarization spreads down the axon. Meanwhile, the first part of the membrane repolarizes. Because Na+ channels are inactivated and additional K+ channels have opened, the membrane cannot depolarize again.
(3) The action potential continues to travel down the axon
Where are action potentials initiated on the neuron?
Action potential can be generated at any point in the neuron’s membrane; but the signals transmitted through the axon are initiated at the hillock
What is saltatory conduction of action potentials?
Saltatory conduction describes the way an electrical impulse skips from node to node down the full length of an axon, speeding the arrival of the impulse at the nerve terminal in comparison with the slower continuous progression of depolarization spreading down an unmyelinated axon.
Synapses are the junctions between two nerve cells. Describe the passing of nerve impulses between nerve cells.
(1) Neurotransmitter stored in vesicles inside axon
(2) neurotransmitter released into synapse
(3) neurotransmitter attaches to the receptor on the dendrite of the next neuron
Nerve impulses pass by:
Diffusion of a neurotransmitter or by changes in the electrical charges of the receiving cell membrane
Compare electrical and chemical synapses.
In an electrical synapse, the plasma membranes of the presynaptic and postsynaptic cells make direct contact. Ions flow through gap junctions that connect the two membranes, allowing impulses to pass directly to the postsynaptic cell.
In a chemical synapse, the plasma membranes of the presynaptic and post-synaptic cells are separated by a narrow synaptic cleft. Neurotransmitter molecules diffuse across the cleft and bind to receptors in the plasma membrane of the postsynaptic cell. The binding opens channels to ion flows that may generate an impulse in the postsynaptic cell.
Chemical and electrical signals interact with structures located on the cell membrane or in the interior of the cell. They include:
(1) Voltage-gated ion channels
(2) Ligand-gated ion channel receptors
(3) Membrane receptors: seven transmembrane G-protein coupled receptors
Compare voltage-gated and ligand-gated ion channels.
Voltage-gated channels open with charge change
Ligand-gated channels open when neuroreceptors bind to binding site on channel
Most neurons receive a multitude of excitatory and inhibitory signals. The signals that leave the hillock and finally reach the axon’s terminals, are the sum of excitatory and inhibitory signals.
Compare Excitatory Post Synaptic Signals (EPSP) and Inhibitory Post Synaptic Signals (IPSP).
EPSP= high excitatory signal + low inhibitory signal
IPSP = low excitatory signal + high inhibitory signal
Are all cells excitable?
All cells have membrane potential but, only neurons, muscle, and endocrine cells are excitable
The nervous system (NS) is divided into what two components?
The central nervous system (CNS) and the Peripheral nervous system (PNS)
How are the PNS and CNS connected?
The PNS connect the CNS to the limbs and organs; relay between the brain and spinal cord and the rest of the body
The PNS can be divided into:
(1) The somatic NS
(2) The autonomic NS
What is the autonomic nervous system?
Component of the PNS responsible for the function of organs outside voluntary control (heart, digestion); a self-regulating system
How is the SNS different from the PNS?
The SNS is under voluntary control;
transmits signals from the brain to end organs such as muscles
The sensory NS is part of…
the SNS; transmits signals from senses such as taste and smell to the spinal cord and brain
The automatic nervous system exerts involuntary control over smooth muscle and glands. What are the two divisions within the system?
Sympathetic and parasympathetic
What phylums have diffuse nerve nets retained from early evolutionary stages?
Every phylum, including the chordates (fish)
In vertebrates, nets take the form of a nerve plexus:
Branching network of intersecting nerves composed of afferent and efferent fibres; and arise from the merging of anterior spinal nerves. The nerves that arise from the plexuses have both sensory and motor functions.
How do the CNS and PNS differ in protection?
Unlike the CNS, the PNS is not protected by the vertebral column and skull, or by the blood-brain barrier
What is the role fo ganglia in the PNS?
relay stations; cluster of neural bodies outside the central nervous system
Compare spinal, dorsal root, and automatic ganglia.
Spinal ganglia are positioned along the spinal cord (at the dorsal and ventral roots of a spinal nerve).
Dorsal root ganglia: the posterior root carries afferent sensory signals to the brain and the ventral root is the efferent motor root.
Automatic ganglia: sympathetic, parasympathetic, enteric division
What is the Enteric Nervous System (ENS)?
Division of the ANS; a mesh-like system of neurons that governs the function of the gastrointestinal tract
Plexus of the ENS are connected into what two types of ganglia?
Auerbach’s and Meissner’s
How does the ANS receive and transmit signals? What is the circuit composed of?
Relay neurons are interneurons that connect sensory neurons to motor neurons.
The circuit is composed of:
- sensory neuron
- interneuron
- motor neuron
- the effector that produces a response
Describe the neurons of the automatic pathways.
Hint: think of a picture
Neuron of CNS connected to the automatic ganglion of PNS by the preganglion neuron; preganglionic neurotransmitter transfers signal.
Postgangiolic neuron releases postganglionic neurotransmitter to the effector organ that carries out the response.
In the sympathetic and parasympathetic divisions of the ANS, they are each considered…
The sympathetic division is considered the ‘fight or flight’ system and the parasympathetic division is considered the ‘rest and digest’.
What effects are controlled by the parasympathetic division and where in the body does this take place?
cerebrum (brain): constricts pupils, increases saliva production, reduces heart rate, constricts bronchia, stimulates the activity of the digestive organs, stimulates the activity of the pancreas, and stimulates the gal bladder
sacral (spinal cord): constricts urinary bladder and stimulates erection of genitals of man and woman.
What effects are controlled by the sympathetic division and where in the body does this take place?
cervical (spinal cord): dilates pupils and inhibits saliva production
thoracal (spinal cord): dilates bronchia, raises the heart rate, inhibits the activity of the digestive organs, inhibits the activity of the pancreas, inhibits the gallbladder
lumbal (spinal cord): inhibits the gall bladder, stimulates the adrenal medulla to release adrenaline and noradrenaline, relaxes urinary bladder, and stimulates orgasm in genitals of man and women
In most cases, both the sympathetic and parasympathetic systems have opposite actions. However, in some cases…
both divisions are involved;
the ‘fight or flight’ system and the ‘rest and digest’ system
Although in some cases both divisions work in synergistic way: meaning they enhance the same effects.
How many and what different neurotransmitters are needed to elicit most of the ANS controlled responses?
Mainly two: acetylcholine (ACh) and norephinenphrine (NE)
their effects depend on the specialization of the effector organ
- both neurotransmitters are examples of the principle of “same key, different locks”
Compare Nicotinic cholinergic receptors (nAChR) and Muscarinic cholinergic receptors (mAChR).
Hint: ACh => cholinergic receptors => nAChRs & mAChRs
nAChRs are ligand-gated ion channels, which evoke rapid depolarization responses to elicit neuronal excitation or skeletal muscle contraction. On the other hand, mAChRs are representative G-protein-coupled receptors that mediate slow effects of ACh.
Nicotinic receptors function within the central nervous system and at the neuromuscular junction. While muscarinic receptors function in both the peripheral and central nervous systems, mediating innervation to visceral organs.
Describe Cholinergic signalling in the ANS.
Preganglionic axons secrete ACh that binds to nAChRs in the ganglion of both divisions of the ANS.
The adrenal medulla is considered a ganglion of the ANS: in the sympathetic nervous system some ACh binds to here.
Explain the statement: the terminal effects of the neurotransmitters are tissue specific.
Postganglionic axons of the sympathetic division secrete norepinenphrine (NE) that binds to adrenergic receptors in all organs; with the exception of the sweat gland where the postganglionic axons secrete ACh.
In skeletal muscle there are no ganglion, ACh binds directly to muscular nicotonic cholinergic receptors (mAChRs).
What does the acronym SLUDDSA stand for when summarizing the functions of the parasympathetic nervous system?
Salivation
Lacrimation
Urination
Digestion
Defecation
Sexual Arousal
What is the adrenal medulla and its purpose?
A modified sympathetic ganglion found on the top of the kidneys. Like other sympathetic ganglia, the adrenal medulla is supplied by cholinergic preganglionic sympathetic fibres that secrete ACh.
The adrenal medulla secretes the hormone epinephrine that binds to adrenergic receptors.
What are the circulatory and metabolic effects of epinephrine?
Epinephrine binds both a and B adrenergic receptors:
Vasoconstriction through a-adrenoreceptors
Vasodilation through B-adrenreceptors
Describe the occurence of the ‘fight or flight’ response.
The response is triggered by the release of norepinephrine and epinephrine:
the immediate reaction is through a-receptors– stimulates smooth muscle contractions and vasoconstriction in the skin and abdominal viscera.
The massive discharge of epinephrine activates the B-receptors– the increase in Ca2+ stimulates heart muscle contraction, blood flow, relaxation of smooth muscle and glycogenolysis
List the physiological effects of the ‘fight or flight’ response.
Hint: there’s nine (2 heart, 2 circulatory, 2 lungs, 1 liver, 1 skin, 1 eyes)
Increased heart rate, dilation of coronary blood vessels, dilation of blood vessels serving muscles, constriction of blood vessels serving digestion, dilation of bronchi, increased respiration rate, increased conversion of glycogen to glucose, skin becomes pale or flushed as blood flow is reduced and dilation of pupils
What is the compensatory mechanism in the ANS?
In times of danger, the sympathetic system prepares the body for violent activity. The parasympathetic system reverses these changes when the danger is over. The compensatory mechanisms returns the body function with actions that do not require immediate reaction back to normal after they have been altered by the sympathetic stimulation.
List the 5 physiological responses of compensatory mechanisms in the ANS.
(1) Slowed rate of the heartbeat
(2) Lower blood pressure
(3) Constrict the pupils
(4) Increase blood flow to the skin and viscera
(5) Cause peristalsis of the GI tract
True or false? Both the sympathetic and parasympathetic systems act on the same organs with similar actions.
false; opposing actions
Note: view Tables 5-2, 5-3, 5-4, 5-5 at the end of lecture 5
Summarizes the:
effects of the autonomic nervous system on various organs and organ systems
sites of release for Acetylcholine and Norepinephrine
Location of Nicotinic and Muscarinic Cholinergic receptors
Comparison of the Autonomic and the somatic nervous systems
The five basic human senses classically recognized include: touch, sight, hearing, smell, and taste. A six sense is presently recognized as…
Proprioception:
Also referred to as kinesthia, the sense of spatial awareness, self-movement, and body position
What are two external senses that are found in some other organisms?
Electroception: the ability to detect weak naturally occurring electrostatic fields in the environment
Magnetoreception: the ability of some organisms to detect Earth’s magnetism
What is the Internal Sensory System?
Interoceptors gather information to control homeostasis
Pressure: baroreceptors and osmoreceptors
Chemicals: CO2, O2, and Glucose
What comprises the sense receptors of the Somatosensory system?
Exteroreceptors: located in discrete exteroceptors organs: detect information directly from outside the body that reach conscience
Interoreceptors (located in the internal organs) and proprioceptors: provides sensory information to the central nervous system (CNS) that do not reach consciousness
Name the seven sensory receptors and their functions.
Mechanoreceptors: transduce mechanical energy
Photoreceptors: respond to visible light energy
Thermoreceptors: respond to changes in temperature
Nociceptors (pain receptors): respond to extreme heat, cold, and pressure, as well as to certain molecules such as acids
Electromagnetic receptors: detect radiation within a wide range of the electromagnetic spectrum
Chemoreceptors: respond to specific chemicals (Interioceptors and exterioceptors)
Proprioceptors: respond to kinesthetic sense, provides information on the relative positions of the parts of the body
Define sensory transduction.
Sensory transduction—the translation of the sensory stimulus into neuronal activity—involves neurons and specialized epithelial cells
Incoming stimuli is converted into neural signals.
More details:
When the neuron acts as the sensory receptor the stimulus is applied to the dendrites and the action potential then travels down sensory neuron and thus is sent to the CNS.
But when there are specialized epithelial cells involved a modified pathway is taken.
Stimulus occurs on the sensory receptor epithelial cell and thus releases a neurotransmitter. This neurotransmitter is bound with the dendrites of the sensory neuron and action potential carries the signal to the CNS.
What is the role of ion channels in sensory transduction?
Ion channels can also respond to extreme heat or cold, pressure, and certain molecules such as acids
Sensory receptors can also be free nerve endings of afferent dendrites. Explain.
In sensory receptors consisting of the dendrites of afferent neurons, a stimulus causes a change in membrane potential that generates action potentials in the axon of the neuron. Examples are pain receptors and some mechanoreceptors.
What are mechanoreceptors?
Touch and pressure receptors in vertebrates that detect mechanical stimuli
What are the four main types of mechanoreceptors
(1) embedded in skin and other surface tissues
(2) skeletal muscles
(3) blood vessel walls
(4) internal organs
What are Merkel cells?
Also known as Merkel-Ranvier cells or tactile epithelial cells:
specialized oval-shaped nondendritic mechanoreceptors essential for light touch sensation
What is the lateral line system in fishes?
The lateral line system consists of a row of neuromasts; vertical section through the skin and lateral line canal
What are invertebrate statocysts?
inertial-sensing organs; typically fluid- or gel-filled sacs of tissue lined with hair cells and containing one or more small calcified masses called statoliths
Describe the human vestibular apparatus inside the ear.
Note: view the slides in lecture 6 to see the parts of the ear
Consists of three semicircular canals and two chambers, the utrivle and the saccule, filled with fluid called endolymph.
The semicircular canals are responsible for perceiving the position and motion of the head:
- essential for maintaining equilibrium and
- coordinating head and body movements
What is acceleration sense and how does it function?
The sense of correcting speed for a hazard, junction or bend without needing to brake pedal.
The otolith organs allow us to sense the direction and speed of linear acceleration and the position (tilt) of the head.
The semicircular canals allow us to sense the direction and speed of angular acceleration.
What are proprioceptors?
Mechanosensory neurons located within muscles, tendons, and joints
What are golgi tendon organs?
Proprioceptors in the tendon adjacent to the myotendinous junction.
Signals are integrated by the CNS with information visual and vestibular information, create an overall representation fo body position, movement, and acceleration.
Name the parts of the single-lens eye.
See lecture 6.1
What is photoreception?
Photoreception refers to mechanisms of light detection that lead to vision.
What are the photoreception components of the retina?
Consists of several layers of neurons interconnected by synapses supported by an outer layer of epithelial pigmented photoreceptor cells
Describe the structure of photoreceptors.
See diagram in lecture 6.1
What are retinal and opsin and their roles in the phototransduction system?
Retinal is a chromophore derived from vitamin A that absorbs energy from light.
Opsin is associated to a G-protein-coupled receptor located in the membrane of rods and cones: captures zero mass electromagnetic particles
True or false? Light activates rhodopsin.
True
Describe opsins in detail.
Opsin are seven transmembrane receptors covalently bound to retinal (rhodopsin in rods, photopsins in cones). Opsins can be found associated with three different G-proteins, termed transducins (Or Gt)
Each type of tranducin determines a wavelength absorbed that can respond to what three colours of light?
red, green. and blue
In the dark the photoreceptor (rod or cone) __________ is continuously released. What is the purpose of this reaction?
Na+ channels open and depolarize the cell and glutamate is released.
In the absence of light, the membrane potential in the postsynaptic cell is in what state?
slightly depolarized state
