BIO 152 Exam 2 Study Materials - Key Terms & Definitions

What does the signaling cell do?

Releases signaling molecules (ligands)

What does the responding cell do?

has receptor proteins that bind to the signaling molecule

What does the release of a signaling molecule affect?

Only certain cells in the body, some more than other

Clarifications about releasing a signal for intercellular communication

- There must be a receiving cell with functioning receptors for a signal to work

- Only cells with that receptor will respond

Clarifications about the signaling and receiving cell

- They can be the same cell (autocrine signaling)

- They can be far apart (endocrine signaling)

- They can be in different organisms (pheromone signaling)

Clarifications about the signaling switch for the responding cell

The amount of signal and type of receptor can cause different degrees of response in the responding cell

What is homeostasis?

Maintaining a stable internal environment

What does homeostasis involve?

Cells communicating and cooperating

What does a sensor do?

Determine stimulus value

What does the integrator do?

Compare the stimulus value to the setpoint

What does the effector do?

Change the conditions

Steps of homeostasis

1. Stimulus

2. Sensor/Receptor

3. Integrator/Controller

4. Effector

Clarifications about how variables are regulated by homeostasis

- Some variable are not regulated (conforming)

- Not all regulation is homeostasis

Clarifications about sensors, controllers, and effectors being unique organs/cells

- A cell, tissue, or organ can be both a sensor and a controller or a controller and effector

- A homeostatic system can have more than one type of sensor, controller, and effector

Clarifications about effectors releasing hormones

- Hormones are a type of signal

- Effectors are what produce a response that directly causes a change in the stimulus

Clarifications about a set point being a constant value

- Set points can be a range

- Set points can be changed by the body

Steps of a negative feedback loop

1. Sensor

2. Integrator

3. Effector

Negative feedback changes a variable to be?

Higher/lower

Clarifications about all feedback being negative feedback

Positive feedback is where feedback causes a stimulus to change in the same direction (higher to higher or lower to lower)

Clarifications about negative feedback always lowering a stimulus

- "Negative" refers to the direction of the response in relation to the stimulus

- If the stimulus is too low, the response is to make the stimulus higher

Clarifications about all negative feedback being homeostasis

Negative feedback can be a response to a stimulus that is not a regulated part of the internal environment

Endotherms

- Able to be active in cold temperatures

- Requires higher metabolic costs (more food)

Ectotherms

- Reliant on external environment

- Lower metabolic costs (less food)

Types of signals

- Small molecules (amino acids)

- Proteins & peptides (insulin)

- Steroids (lipids)

- Endogenous vs Exogenous ("normal" vs drug/toxin)

What do micelles look like?

Hydrophobic inside (heads on outside, tails on inside)

What do micelles do?

Store lipid signals

What do vesicles look like?

Hydrophilic inside (heads to tails, tails to heads)

What do vesicles do?

Store hydrophilic signals

What do signals release by exocytosis do?

- Vesicles/micelles fuse with plasma membrane

- Interior of vesicle is released into extracellular fluid

Types of signalling

- Endocrine

- Paracrine

- Autocrine

- Direct

What is autocrine signaling?

Signaling and responding cells are the same cell

What is direct signaling?

Gap junctions/plasmodesmata - passages between plasma membranes

What is endocrine signaling?

Through the bloodstream - requires bulk transport

What is paracrine signaling?

Nearby - about 20 micrometers or less (a few cells away)

What is the difference between endocrine and paracrine signaling?

Endocrine signaling uses bulk transport (such as blood) while paracrine signaling uses diffusion

Example of paracrine signaling

Neurons cause muscles to contract at the neuromuscular junction

Example of autocrine signaling

Interferon release by viral-infected cells induces the same cell to undergo apoptosis

Example of endocrine signaling

In the medaka fish digestive tract, islet of the pancreas release insulin into the bloodstream. The insulin travels to liver cells that respond to insulin

Example of direct signaling

Multiple cardiomyocytes (heart muscle cells) are connected by a gap junction

What are receptors

Proteins on/in a cell

Examples of receptors

- Cell surface proteins

- Intracellular receptors

What does the ligand (signal) bind to

The shape of the active site

Steps of receptor activation

1. Receptor inactive (no ligand bound)

2. Ligand binds to receptor (temporarily)

3. Conformational change (change in shape of receptor)

4. Singla transduction: Receptor activation leads to activity in cell

Types of receptors

- Intracellular receptor

- G-protein coupled receptor

- Ligand-gated ion channel

- Enzyme-linked receptor (receptor Kinase)

What type of signaling molecule is non-polar

Steroid

Steps of an intracellular receptor

1. Hormone goes through plasma membrane, binds to receptor, receptor changes shape

2. Receptor migrates to nucleus

3. Gene expressed

Where are cell surface receptors located

plasma membrane

What do cell surface receptors receive

hydrophilic signals

What is the extracellular domain

binding site for ligand

What is the transmembrane domain and what does it do

hydrophobic amino acids, transduces signal to inside

What does the intracellular domain do

causes a cellular effect

What are ion-channel linked receptors dependent on

Ca++ for muscle contraction

What are the types of ion channels

- Ligand gated

- Mechanically gated

- Always open

- Voltage-gated

When a protein changes shape, it

must be destroyed because it no longer works

What does activated adenylyl do in G-protein activation

converts ATP into the second messenger cAMP, which in turn activates protein kinase A

What does activated protein kinase A do in G-protein activation

phosphorylates proteins in the heart muscle, causing the heart rate to increase

What does cAMP act as

second messenger, binds to enzymes to activate/inactivate them

Steps of going from ATP to cyclic AMP

ATP - Adenylyl cyclase - cAMP

What does each member of the receptor pair do in enzyme linked receptors

each member of the receptor pair attaches phosphate groups to the other member

What does the phosphate group do in enzyme linked receptors

provide binding sites for intracellular signaling proteins

Steps to activating a receptor

1. Receptor is inactive

2. Receptor dimerizes

3. Receptor autophosphorylates

4. Signal transduction leads to activation of second messengers

What is a kinase?

Enzyme that transfers phosphate to a protein (phosphorylates)

What is a phosphatase

Enzyme that removes phosphate from protein (dephosphorylates)

What does phosphorylation cascade allow

allows for integration of signals from different sources

Which organisms have cellular communication?

All complex multicellular organisms

What are nervous systems found in?

Only animal, not protists, plants, fungi

What do all eukaryotic cells have

electrical difference across membrane

What does a negative charge inside a cell help do

helps move cations into the cell against a concentration gradient (Na/K/ATPase pump)

What is the first even in nervous system evolution

Neurons in a nervous system - use changes in electrical charge to transmit signal within a cell, then use paracrine signaling/gap junctions between cells

In what organisms is a nerve net found?

sea anemones, jellyfish, comb jellies

What do jellyfish, comb jellies, and sea anemones not have

central nervous system

What is the structure of a nerve net

- Sensory neurons: detect stimuli, output to motor neurons

- Motor neurons: input from sensory neurons, output to muscles

What do pacemaker neurons do in jellyfish

create rhythmic electrical signals that do not require input

What are ganglion

group of neurons in communication with each other

What are internuerons

neurons between sensory and motor neurons

What do ganglia allow for

allows for processing of information

Steps of information processing

1. sensory neuron

2. interneurons

3. motor neurons

What are ganglia, centralization & cephalization in

bilateral animals

What is centralization

localization of ganglia in central part of the body

Types of nerve cords with ganglia

- Ventral nerve cord: most invertebrates

- Dorsal nerve cord (spinal cord): vertebrates

What do pacemaker neurons help with in centralization

movement

What is cephalization

large ganglion in the head

What organisms have more/less cephalization

- More: mammals

- Less: insects

The adult starfish has ganglia in each arm connected by a ring, but no brain. This shows...

Centralization

What does a sea anemone have

nerve net

What does a flatworm have

eyespots, paired ganglia, ventral nerve cord

What does an earthworm have

brain, ventral nerve cord, segmental ganglion

What does an insect have

brain, eye, ventral nerve cord

What does a squid have

brain, giant axon

What does a frog have

eye, brain, dorsal spinal cord, nerves

What are the functions of the neuron?

- Convert chemical signals (neurotransmitters) into electrical signals (postsynaptic potentials/graded potentials)

- Merging (convergence) of multiple signals

- Creation of a regenerating electrical signal (action potential)

- Transmission (propagation) of electrical signals

- Convert electrical signals into chemical signals

What does the axon do

Conducts action potential

What does the axon hillock do?

- Initiates action potential

- Convergence of multiple signals

What does the axon terminal do?

Converts electrical signal to chemical signal

What does the cell body (soma) do?

Basic cellular functions

What do the dendrites do?

Converts chemical signal to electrical signal

Anatomy of the neuron

Specific flow of information through neurons

1. Neurotransmitters cross synapse to receptors on dendrites

2. Ligand-gated ion channels open on dendrites, starting electrical signal

3. Electrical signal spreads passively down dendrites to converge at the axon hillock

4. Axon hillock- multiple electrical signals from different dendrites converge, add up

5. If high enough electrical signal at hillock, action potential starts

6. Action potential travels down axon in one direction to the axon terminal

7. At axon terminal, action potential causes neurotransmitters to be released

What do sensory neurons have and what do they do?

Specialized endings, receive sensory input

What do motor neurons have?

Many branching dendrites, axon muscle/gland