Chedrese– Week 1 to 5

Question 1

Metazoa includes all organisms in the animal kingdom; break this down into two subkingdoms and explain their differences.

Answer 1

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.

Question 2

What is a Protista? What is their significance in studying evolution?

Answer 2

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.

Question 3

Unicellular protists with more animal-like characteristics can be referred to as ______, though this term is increasingly incommon.

Answer 3

Protozoa

Question 4

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)?

Answer 4

Choanoflagellates

Question 5

What are sponges?

Answer 5

Sessile, aquatic animals (and the closest relative of the choanoflagellates) of the subkingdom/suborder parazoa and phylum Porifera.

Question 6

How do sponges consume nutrients?

Answer 6

Sponges feed through phagocytosis of individual cells (called filter feeding)

Question 7

How do sponges communicate?

Answer 7

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.

Question 8

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.

Answer 8

(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

Question 9

What allows cells to recognize and bind to one another?

Answer 9

A common proteome of identical proteins

Question 10

What are the (2) hallmarks of multicellularity?

Answer 10

(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

Question 11

Describe the flow of sodium and potassium through animal body fluids and tissue compartments.

Answer 11

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

Question 12

Describe the Extracellular Matrix (ECM).

Answer 12

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

Question 13

How are the cuticles of worms and insects and the shells of mulluscs formed?

Answer 13

Sheet-like depositions of ECM form the basement membranes on which various epithelial cells rest

Question 14

True or false? Nearly all animals undergo some form of sexual reproduction.

Answer 14

True; some animals can reproduce asexually but it is uncommon

Question 15

Fertilization is the fusion of sperm and egg to produce a new organism. Describe the process in detail.

Answer 15

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.

Question 16

Define zygote.

Answer 16

a diploid cell resulting of fertilization

Question 17

Define blastomeres.

Answer 17

daughter cells of the dividing zygote

Question 18

What is a morula?

Answer 18

a compact mass of cells derived from the blastomeres (or daughter cells of the zygote)

Question 19

What form follows fertilization and the morula?

Answer 19

Morula derives into a hollow sphere of single layer of cells called the blastula

Question 20

What are the two main events that occur at the stage of morula?

Answer 20

(1) Compaction
(2) Expression of the Na+/K+ -ATPase (high concentration solute draws in water)

Question 21

Describe the process of blastulation of the embryo/blastula.
Hint: hemispheres

Answer 21

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)

Question 22

Compare Protostomia and Deuterostomia.

Answer 22

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.

Question 23

What cleavage do Protostomia exhibit and what are some organisms that establish this way?

Answer 23

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

Question 24

What cleavage do Deuterostomia exhibit and what are some organisms that establish this way?

Answer 24

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)

Question 25

What is the Inner cell mass (ICM) of deuterostomes?

Answer 25

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.

Question 26

What is the Gastrula and how is it formed?

Answer 26

The structure of cell differentiation composed of the ectoderm, mesoderm, and endoderm. The blastula invaginates and further differentiates into these three germ layers.

Question 27

The ectoderm, mesoderm, and endoderm give rise to what bodily structures?

Answer 27

Ectoderm: skin and nervous system
Mesoderm: muscles and skeleton
Endoderm: digestive tract

Question 28

Describe the Primitive Streak.

Answer 28

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.

Question 29

Describe the location, structure, and function of the Coelom.

Answer 29

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.

Question 30

Mesenchyme tissue gives rise to which cell layer? Describe it’s structure and purpose.

Answer 30

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).

Question 31

The interactions between _________ and _________ contribute to form nearly every organ in the body.

Answer 31

mesenchyme and epithelium

Question 32

Compare the blastopore and archenteron.

Answer 32

The blastopore is the opening of the invagination and the archenteron is the structure/substance of the inner body cavity (coleum).

Question 33

The development of the mesoderm induces the growth of what other structures?

Answer 33

The neural plate, precursor to the nervous system, the notochord, and [missed]

Question 34

What is a notochord?

Answer 34

A flexible rodlike structure that serves as a primary longitudinal structural element of the phylum cordate (spinal cord)

Question 35

Animals have three primary embryonic cell layers. What are they and how do they arise?

Answer 35

Ectoderm, mesoderm, and endoderm
PGCs arise from a population of pluripotent cells in the ectoderm.

Question 36

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.

Answer 36

Diploblasts; Cnidaria and Ctenophora (jellyfish, corals, hydra)

Question 37

What are the first 5 stages in Triploblastic organism development?

Answer 37

(1) Fertilization
(2) Cleavage
(3) Gastrulation
(4) Organogenesis
(5) Neurulation

Question 38

What is organogenesis and terminal differentiation?

Answer 38

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

Question 39

What is the notochord, its origin, and purpose?

Answer 39

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.

Question 40

The notochord defines a specific phylum. Which is it? How does the notochord structure differ in fishes and amphibians specifically?

Answer 40

Chordata;
persists in the trunk and tail of fishes and amphibians

Question 41

How does the notochord provide body support?

Answer 41

Contains the nerve cord which is the main communication stem of the nervous system.
The gastrointestinal tract is below.

Question 42

During development, what structure replaces the notochord?

Answer 42

Hollow interlocking vertebra and cartilaginous substances between vertebrae called intervertebral discs

Question 43

What is the initial major event of organogenesis?

Answer 43

Neurulation

Question 44

What is neurulation and describe the development process.

Answer 44

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.

Question 45

After the stage of neurulation, what is the embryo called?

Answer 45

neurula

Question 46

Describe neural tube formation.

Answer 46

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).

Question 47

During neurulation, the body develops into segments with specialized functions. What are these segments called and describe their structure.

Answer 47

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)

Question 48

What are ganglia and their function?

Answer 48

Clusters of nerve cell bodies and function like relay stations with chemical messages

Question 49

What is the ocelli and how is it unique in jellyfish?

Answer 49

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)

Question 50

Describe neurogenic signalling or contraction.

Answer 50

contraction of the heart or heart-like muscles through electrogenic stimulation

Question 51

Describe the nervous systems of Echinoderms.

Answer 51

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

Question 52

In what organisms did a true central nervous system first evolve?

Answer 52

A true CNS first evolved with bilateral symmetry in segmented animals (arthropods, annelids, chordates)

Question 53

What is cephalization?

Answer 53

An evolutionary trend in which the mouth and sense organs become concentrated at the front end of an animal.

Question 54

What are the advantages of cephalization?

Answer 54

Sensory information about the environment is initially detected in the anterior region:
Detect images, developed learning abilities, and memory and ultimately self-awareness

Question 55

The most advanced invertebrate brains are found in which organisms?

Answer 55

cephalopod mollusks (squid, octopi, cuttlefish, etc)

Question 56

Define vertebrates.

Answer 56

Comprise all animals with an internal skeleton

Question 57

All vertebrates are built along the basic chordate body plan that comprise:

Answer 57

• the skull
• a vertebral column
• the spinal cord
• ganglia
• nerves

Question 58

The central nervous system (CNS) is divided into what two major parts?

Answer 58

the brain and the spinal cord

Question 59

The brain lies within the skull and consists of four principle parts:

Answer 59

(1) Brain stem
- midbrain
- pons
- Medulla oblongata
(2) Cerebrum
(3) Cerebellum
(4) Diencephalon
- thalamus and hypothalamus

Question 60

The Hypothalamus derives from which part of the brain? Where is it located?

Answer 60

Derives from the diencephalon
Located below the thalamus, extend to the pituitary gland

Question 61

Describe the structure of the vertebral column and the spinal cord.

Answer 61

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.

Question 62

What is cerebrospinal fluid (CSF)?

Answer 62

The CSF is a clear, colourless body fluid found in the brain and spinal cord that is produced by glial cells in the brain.

Question 63

What is the blood-brain barrier (BBB) and its purpose?

Answer 63

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.

Question 64

What is the skull and its latin name?

Answer 64

Cranium
A bony structure that forms the head in vertebrates

Question 65

Do insects and invertebrates have skulls?

Answer 65

no.

Question 66

The nervous system is composed of two types of cells. What are they and their functions?

Answer 66

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.

Question 67

What are the three types of neurons?

Answer 67

motor, sensory, and Purkinje (also known as central neurons)

Question 68

What are the nodes of Ranvier?

Answer 68

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.

Question 69

Define nerves.

Answer 69

Enclosed cable-like bundles of axons surrounded by three layers of connective tissue

Question 70

How are nerves classified?

Answer 70

(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

Question 71

What are Ganglia (or a ganglion) and its function?

Answer 71

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.

Question 72

Where are the ganglia located in vertebrates?

Answer 72

Located along the spinal cord at the dorsal and ventral roots of the spinal nerve

Question 73

There are 31 pairs of spinal nerves along the human vertebral column that are organized into plexus. What are they?

Answer 73

Cervical, Thoracic, Lumbar, Sacral, and coccygeal

Question 74

What are cranial nerves?

Answer 74

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.

Question 75

What is the 10th cranial nerve and why is it important?

Answer 75

the Vagus nerve is found in many parts of the body

Question 76

________ pituitary is mainly nerve tissue and _______ pituitary is mainly glandular (hormonal) tissue.

Answer 76

posterior; anterior

Question 77

Communication in the animal body has three main components:

Answer 77

(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)

Question 78

Molecules secreted into the body fluids binds to what protein receptors?

Answer 78

ligands

Question 79

What are endocrine glands?

Answer 79

organs that produce and secrete chemical signals (termed hormones)

Question 80

What are neurons?

Answer 80

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)

Question 81

What are hormones?

Answer 81

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

Question 82

What are neurotransmitters?

Answer 82

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

Question 83

The neurotransmitters termed monomines are derived from…

Answer 83

amino acids

Question 84

The neurotransmitter Acetylcholine is derived from…

Answer 84

acetyl-CoA

Question 85

What are two membrane-soluble chemical signals?

Answer 85

Thyroid hormones and aldosterone

Question 86

What is homeostasis?

Answer 86

The tendency to maintain a stable, relative constant internal environment

Question 87

What are the 6 physical and chemical variables of homeostasis?

Answer 87

(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

Question 88

What two organs that maintain homeostasis?

Answer 88

The hypothalamus and the pituitary gland

Question 89

What is feedback regulation? What are two mechanisms of control?

Answer 89

Environmental influences on body variables

Mechanisms of control: Negative and positive feedback regulation

Question 90

What are at four interdependent components for a regulated variable in the negative feedback cycle (ex: the temperature regulatory system)?

Answer 90

(1) set point
(2) sensor
(3) integrator
(4) effector

Question 91

In the regulation of body temperature, what is activated by the cold?

Answer 91

Shivering, hunger, increased voluntary activity, increased secretion catecholamines, decreased heat loss, cutaneous vasoconstriction, curling up, and horripilation

Question 92

In the regulation of body temperature, what is activated by the heat?

Answer 92

Increased heat loss, cutaneous vasodilation, sweating, increased respiration, decreased heat production, anorexia, apathy and inertia

Question 93

Give two examples of positive feedback cycles.

Answer 93

Hormonal and neural regulation of glycemia & childbirth/breastfeeding

Question 94

What are endocrine glands?

Answer 94

Organs that produce and secrete chemical signals termed hormones into the ECF then general circulation

Question 95

What are exocrine glands? Give a few examples.

Answer 95

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

Question 96

Name the principles of electrical signalling in the nervous system.

Answer 96

(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

Question 97

Why is the giant squid used for its axons as a research model?

Answer 97

Very large and thick axons; unmyelinated

Question 98

At rest, what is the differences in charges between the interior and exterior of the membrane?

Answer 98

ranges from -40mV to -80mV

Question 99

What are three main components that contribute to membrane polarization?

Answer 99

(1) Na+/K+ -ATPase pump
(2) ion channels
(3) large negatively charged proteins

Question 100

If the membrane is like a battery, how is it recharged?

Answer 100

The Na+/K+ -ATPase pump transports 3 Na+ out for every 2 K+ moved into the cell

Question 101

What are Na+/K+ concentrations, relatively, at rest and what is the concentration gradient?

Answer 101

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

Question 102

Ion channels (ATP-dependent ion pump) creates a ________ intramembrane environment, and a concentration gradient, or electrical force, on ______ side(s) of the membrane.

Answer 102

negative; both

Question 103

Large and negatively charged proteins (anions) are more abundant…

Answer 103

inside of the cell (because they are too large to leave); creating a intercellular negative environment

Question 104

What are the two basic roles of the membrane potential?

Answer 104

(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

Question 105

Describe the role of the voltage-gated Na+ channels in depolarization.
Hint: briefly describe how the channel functions

Answer 105

(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

Question 106

Describe the role of the voltage-gated K+ channels in depolarization.
Hint: voltage-gated K+ channels also termed leaking channels

Answer 106

At rest, the membrane is more permeable to potassium than to sodium.
Potassium tends to easily leak out of the cell

Question 107

Describe the ion channels at resting potential.

Answer 107

• K+ and Na+ leak channels are open
• Na+/K+ pumps 3 Na+ out and 2 K+ in
• K+ and Na+ voltage-gated channels closed

Question 108

A weak stimulatory/inhibitory signal causes what graded potentials?
Hint: answer for each situation

Answer 108

A weak stimulatory signal causes graded depolarization.
A weak inhibitory signal causes graded hyperpolarization.

Question 109

What fashion does the membrane polarize in, when the intensity of the stimulus overcomes a threshold?

Answer 109

all or none fashion; depolarization reaches a peak and never goes above the peak regardless of the intensity of the stimulus

Question 110

Summarize the Action Potential Cycle in neurons.

Answer 110

(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

Question 111

Compare absolute and relative refractory periods.

Answer 111

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.

Question 112

What are the two physiological refractory period connotations?

Answer 112

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

Question 113

Describe the signal directionality (or the direction of travel of action potential).

Answer 113

(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

Question 114

Where are action potentials initiated on the neuron?

Answer 114

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

Question 115

What is saltatory conduction of action potentials?

Answer 115

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.

Question 116

Synapses are the junctions between two nerve cells. Describe the passing of nerve impulses between nerve cells.

Answer 116

(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

Question 117

Nerve impulses pass by:

Answer 117

Diffusion of a neurotransmitter or by changes in the electrical charges of the receiving cell membrane

Question 118

Compare electrical and chemical synapses.

Answer 118

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.

Question 119

Chemical and electrical signals interact with structures located on the cell membrane or in the interior of the cell. They include:

Answer 119

(1) Voltage-gated ion channels
(2) Ligand-gated ion channel receptors
(3) Membrane receptors: seven transmembrane G-protein coupled receptors

Question 120

Compare voltage-gated and ligand-gated ion channels.

Answer 120

Voltage-gated channels open with charge change
Ligand-gated channels open when neuroreceptors bind to binding site on channel

Question 121

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).

Answer 121

EPSP= high excitatory signal + low inhibitory signal
IPSP = low excitatory signal + high inhibitory signal

Question 122

Are all cells excitable?

Answer 122

All cells have membrane potential but, only neurons, muscle, and endocrine cells are excitable

Question 123

The nervous system (NS) is divided into what two components?

Answer 123

The central nervous system (CNS) and the Peripheral nervous system (PNS)

Question 124

How are the PNS and CNS connected?

Answer 124

The PNS connect the CNS to the limbs and organs; relay between the brain and spinal cord and the rest of the body

Question 125

The PNS can be divided into:

Answer 125

(1) The somatic NS
(2) The autonomic NS

Question 126

What is the autonomic nervous system?

Answer 126

Component of the PNS responsible for the function of organs outside voluntary control (heart, digestion); a self-regulating system

Question 127

How is the SNS different from the PNS?

Answer 127

The SNS is under voluntary control;
transmits signals from the brain to end organs such as muscles

Question 128

The sensory NS is part of…

Answer 128

the SNS; transmits signals from senses such as taste and smell to the spinal cord and brain

Question 129

The automatic nervous system exerts involuntary control over smooth muscle and glands. What are the two divisions within the system?

Answer 129

Sympathetic and parasympathetic

Question 130

What phylums have diffuse nerve nets retained from early evolutionary stages?

Answer 130

Every phylum, including the chordates (fish)

Question 131

In vertebrates, nets take the form of a nerve plexus:

Answer 131

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.

Question 132

How do the CNS and PNS differ in protection?

Answer 132

Unlike the CNS, the PNS is not protected by the vertebral column and skull, or by the blood-brain barrier

Question 133

What is the role fo ganglia in the PNS?

Answer 133

relay stations; cluster of neural bodies outside the central nervous system

Question 134

Compare spinal, dorsal root, and automatic ganglia.

Answer 134

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

Question 135

What is the Enteric Nervous System (ENS)?

Answer 135

Division of the ANS; a mesh-like system of neurons that governs the function of the gastrointestinal tract

Question 136

Plexus of the ENS are connected into what two types of ganglia?

Answer 136

Auerbach’s and Meissner’s

Question 137

How does the ANS receive and transmit signals? What is the circuit composed of?

Answer 137

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

Question 138

Describe the neurons of the automatic pathways.
Hint: think of a picture

Answer 138

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.

Question 139

In the sympathetic and parasympathetic divisions of the ANS, they are each considered…

Answer 139

The sympathetic division is considered the ‘fight or flight’ system and the parasympathetic division is considered the ‘rest and digest’.

Question 140

What effects are controlled by the parasympathetic division and where in the body does this take place?

Answer 140

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.

Question 141

What effects are controlled by the sympathetic division and where in the body does this take place?

Answer 141

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

Question 142

In most cases, both the sympathetic and parasympathetic systems have opposite actions. However, in some cases…

Answer 142

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.

Question 143

How many and what different neurotransmitters are needed to elicit most of the ANS controlled responses?

Answer 143

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”

Question 144

Compare Nicotinic cholinergic receptors (nAChR) and Muscarinic cholinergic receptors (mAChR).

Hint: ACh => cholinergic receptors => nAChRs & mAChRs

Answer 144

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.

Question 145

Describe Cholinergic signalling in the ANS.

Answer 145

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.

Question 146

Explain the statement: the terminal effects of the neurotransmitters are tissue specific.

Answer 146

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).

Question 147

What does the acronym SLUDDSA stand for when summarizing the functions of the parasympathetic nervous system?

Answer 147

Salivation
Lacrimation
Urination
Digestion
Defecation
Sexual Arousal

Question 148

What is the adrenal medulla and its purpose?

Answer 148

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.

Question 149

What are the circulatory and metabolic effects of epinephrine?

Answer 149

Epinephrine binds both a and B adrenergic receptors:
Vasoconstriction through a-adrenoreceptors
Vasodilation through B-adrenreceptors

Question 150

Describe the occurence of the ‘fight or flight’ response.

Answer 150

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

Question 151

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)

Answer 151

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

Question 152

What is the compensatory mechanism in the ANS?

Answer 152

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.

Question 153

List the 5 physiological responses of compensatory mechanisms in the ANS.

Answer 153

(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

Question 154

True or false? Both the sympathetic and parasympathetic systems act on the same organs with similar actions.

Answer 154

false; opposing actions

Question 155

Note: view Tables 5-2, 5-3, 5-4, 5-5 at the end of lecture 5

Answer 155

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

Question 156

The five basic human senses classically recognized include: touch, sight, hearing, smell, and taste. A six sense is presently recognized as…

Answer 156

Proprioception:
Also referred to as kinesthia, the sense of spatial awareness, self-movement, and body position

Question 157

What are two external senses that are found in some other organisms?

Answer 157

Electroception: the ability to detect weak naturally occurring electrostatic fields in the environment

Magnetoreception: the ability of some organisms to detect Earth’s magnetism

Question 158

What is the Internal Sensory System?

Answer 158

Interoceptors gather information to control homeostasis
Pressure: baroreceptors and osmoreceptors
Chemicals: CO2, O2, and Glucose

Question 159

What comprises the sense receptors of the Somatosensory system?

Answer 159

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

Question 160

Name the seven sensory receptors and their functions.

Answer 160

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

Question 161

Define sensory transduction.

Answer 161

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.

Question 162

What is the role of ion channels in sensory transduction?

Answer 162

Ion channels can also respond to extreme heat or cold, pressure, and certain molecules such as acids

Question 163

Sensory receptors can also be free nerve endings of afferent dendrites. Explain.

Answer 163

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.

Question 164

What are mechanoreceptors?

Answer 164

Touch and pressure receptors in vertebrates that detect mechanical stimuli

Question 165

What are the four main types of mechanoreceptors

Answer 165

(1) embedded in skin and other surface tissues
(2) skeletal muscles
(3) blood vessel walls
(4) internal organs

Question 166

What are Merkel cells?

Answer 166

Also known as Merkel-Ranvier cells or tactile epithelial cells:
specialized oval-shaped nondendritic mechanoreceptors essential for light touch sensation

Question 167

What is the lateral line system in fishes?

Answer 167

The lateral line system consists of a row of neuromasts; vertical section through the skin and lateral line canal

Question 168

What are invertebrate statocysts?

Answer 168

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

Question 169

Describe the human vestibular apparatus inside the ear.

Note: view the slides in lecture 6 to see the parts of the ear

Answer 169

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

Question 170

What is acceleration sense and how does it function?

Answer 170

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.

Question 171

What are proprioceptors?

Answer 171

Mechanosensory neurons located within muscles, tendons, and joints

Question 172

What are golgi tendon organs?

Answer 172

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.

Question 173

Name the parts of the single-lens eye.

Answer 173

See lecture 6.1

Question 174

What is photoreception?

Answer 174

Photoreception refers to mechanisms of light detection that lead to vision.

Question 175

What are the photoreception components of the retina?

Answer 175

Consists of several layers of neurons interconnected by synapses supported by an outer layer of epithelial pigmented photoreceptor cells

Question 176

Describe the structure of photoreceptors.

Answer 176

See diagram in lecture 6.1

Question 177

What are retinal and opsin and their roles in the phototransduction system?

Answer 177

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

Question 178

True or false? Light activates rhodopsin.

Answer 178

True

Question 179

Describe opsins in detail.

Answer 179

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)

Question 180

Each type of tranducin determines a wavelength absorbed that can respond to what three colours of light?

Answer 180

red, green. and blue

Question 181

In the dark the photoreceptor (rod or cone) __________ is continuously released. What is the purpose of this reaction?

Answer 181

Na+ channels open and depolarize the cell and glutamate is released.

Question 182

In the absence of light, the membrane potential in the postsynaptic cell is in what state?

Answer 182

slightly depolarized state