Bio 172 Exam 4

Epithelial Tissue

Covers every surface of the vertebrate body

Can come from any of the 3 germ layers

Some can change into glands

• Provides protective barriers —> not a lot of gaps between cells

Simple Squamous Epithelium

One layer thick

Flat, irregular shape

Lines lungs and blood capillaries

Permits diffusion

Simple Cuboidal Epithelium

One layer thick

About as wide as tall

Lines kidney tubules and several glands

Secretion, absorption, rich in transport channels

Simple Columnar Epithelium

One layer thick

Taller than they are wide

Lines airways of the respiratory tract and most of the gastrointestinal tract

Contains goblet cells

Goblet Cells

Glandular cells that secrete mucus in the respiratory/digestive tract

Found in Simple Columnar Epithelium

Stratified Epithelium

2+ layers thick

Outer layer of skin, lining of mouth

Most common is squamous

Tough layer provides protection

Protective barrier enhanced with keratin

• Reptile scales

Exocrine Glands

Connected to epithelium by a duct

Sweat, sebaceous, and salivary glands

Endocrine Glands

Secretions (hormones) enter the blood

Thyroid, pituitary, liver, pancreas, adrenal glands

Connective Tissue

Arises from the mesoderm

Most diverse and abundant form of tissue

Connect and give support to all other tissues

Have abundant extracellular material called the matrix

Loose Proper Connective Tissue

Support, insulation, food storage, and nourishment

Beneath the skin and between organs

Dense Proper Connective Tissue

Provide flexible and strong connections

Tendons

Special Connective Tissue Types

Bone, Blood, and Cartilage

Cartilage

Tougher than both types of proper connective tissue (greater tensile strength)

Surface of joints, outer ear, nose, etc.

Coated in chondrocyte

Bone

Osteocytes remain alive in a matrix hardened with calcium phosphate

Blood

Extracellular material is the fluid plasma

Erythrocytes - red blood cells

Leukocytes - white blood cells

Thrombocytes - platelets

• Role in blood clotting

Muscle Tissue

Muscles convert chemical energy to mechanical energy

Hallmark of animal evolution

Smooth, skeletal, and cardiac

Myosin

One of the contractile proteins in muscles found even in sponges

Smooth Muscle

Powers rhythmic, involuntary contractions commanded by the central nervous system

Blood vessels, stomach, intestines

Skeletal Muscle

Powers locomotion and other voluntary movements

Usually attached to bone by tendons, so muscle contraction causes bones to move

Cardiac Muscle

Powers rapid spread of signal, initiating contraction (involuntary)

Highly interconnected small cells

Found only in vertebrates; the latest muscle to evolve

Primary Tissues In Vertebrate Body

Epithelial, connective, muscle, and nerve

Organs

Combinations of different tissues that form a structural and functional unit

Organ Systems

Groups of organs that cooperate to perform the major activities of the body

Vertebrate Organ System

11 principal organ systems

Nervous, Endocrine, Skeletal, Muscular, Digestive, Circulatory, Respiratory, Urinary, Integumentary, Lymphatic/Immune, and Reproductive

Groupings of Organ Systems

Communication and Integration —> nervous and endocrine

Support and Movement —> musculoskeletal

Regulation and Maintenance —> digestive, circulatory, respiratory, and urinary

Defense —> integumentary and immune

Reproduction and Development

Nervous System

Detects stimuli and coordinates response

Brain, spinal cord, nerves, and sensory organs

Endocrine System

Sends chemical messages to regulate chemical processes across all organ systems

Musculoskeletal System

Skeletal provides a rigid framework for muscles to pull

Vertebrates → internal skeleton 

Invertebrates → external skeletons

Bone → connective tissue

Respiratory System

Trachea and Lungs

Urinary System

Kidney, ureter, bladder, and urethra

Circulatory System

Transports oxygen, nutrients, and hormones to your body's cells and removes waste products like carbon dioxide

Heart, arteries, veins, and capillaries

Reproduction System

Development of gametes

Allows merging of gametes

In many vertebrates, the female reproductive system is specialized for prolonged nurturing of the fetus 

Negative Feedback Loop

Stimulus → sensor → integrating center → effector → response → sensor

• Stimulus: deviation from set point

• Sensor: constantly monitors conditions

• Integrating center: compares conditions to a set point based on a desired value

• Effector: causes changes to compensate for deviation

• Response: moves the system toward the set point

• Negative feedback back to the sensor

Temperature Regulation in Mammals

Antagonistic effectors are involved in the control of body temperature

If the hypothalamus detects high temperature

• Promotes heat dissipation via sweating and dilation of blood vessels in the skin

If the hypothalamus detects low temperature

• Promotes heat conservation via shivering and constriction of blood vessels in the skin

Fevers

A change in the set point

Caused by pyrogens

Positive Feedbacks

Enhance a change instead of counteracting it

Drives the variable even further from the set point

Rare

Example: Contractions in childbirth

Body Heat =

heat produced + heat transferred 

Radiation

Transfer of heat by electromagnetic radiation 

Conduction

Direct transfer of heat from a hotter object to a colder one

Convection

Transfer of heat brought about by the movement of a gas or liquid

Wind

Evaporation

Heat of vaporization or the amount of energy needed to change a liquid to a gas phase

Ectotherms

Do not use metabolism for heat production

Most invertebrates

Use behavior to regulate temps

Low metabolic rate but not capable of sustained high-energy activity

Endotherms

Create internal metabolic heat

Heat must be dissipated when hot or conserved when cold

Heat transfer is controlled by the amount of blood flow to the surface of the animal

Small animals require a higher metabolic rate than large animals to maintain heat

• Surface area to volume ratio

Allows sustained high-energy activity

Torpor

Reduction of metabolic rate and temperature in endotherms

Change of set point to conserve energy

Hummingbirds every evening

Central Nervous System

Brain and Spine

Command center for the body

Peripheral Nervous System

Collects information and carries out responses

Sensory (Afferent) Neurons

Carry impulses to the CNS (outward to in)

Peripheral Nervous System

Motor (Efferent) Neurons

Carry impulses from the CNS to effectors (muscles and glands) (inside to outside)

Peripheral Nervous System

Interneurons (Association)

Provide more complex reflexes and associative functions

Central Nervous System

Somatic Nervous System

Stimulates skeletal muscles (voluntary) 

Autonomic Nervous System

Stimulates smooth and cardiac muscles, as well as glands (involuntary)

Sympathetic nervous system (fight or flight)

Parasympathetic nervous system (rest and digest)

Schwann Cells

PNS

Produce myelin sheaths around axons 

Myelinated and unmyelinated axons are bundled to form nerves

Oligodendrocytes

CNS

Produce myelin sheaths around axons 

Myelinated axons form white matter

Unmyelinated dendrates/cell bodies form grey matter

Nerve Impulse Transmission

Neurons send electrical signals across cell membranes using electrical potential

A potential difference exists across every cell’s plasma membrane

• Positive pole → extracellular fluid side

• Negative pole → cytoplasmic side

When a neuron is not being stimulated, it maintains a resting potential ( -70mV)

Cytoplasmic Side More Negative… Why?

Sodium-potassium pump

• Brings two K+ into the cell for every 3 Na+ it pumps out

Ion leakage channels

• Membrane is more permeable to K+

• Allows more K+ to diffuse out than Na+ to diffuse in 

The plasma membrane is impermeable to negative ions and molecules (proteins and nucleic acids) 

• Already inside the cell, so difficult for them to exit

Graded Potentials

More localized changes that vary in size based on stimulus intensity

Due to activation of gated ion channels

Can be depolarizing or hyperpolarizing 

• Depolarization makes the membrane potential more positive

• Hyperpolarization makes the membrane potential more negative

Size depends on either the strength of the stimulus or the amount of ligand available to bind to their receptors

Summations → the ability of graded potentials to combine

• Important for triggering action potentials

Action Potentials

Larger, widespread changes that move along axons

Triggered by a threshold change in potential 

Result when depolarization reaches the threshold potential (-55 mV) 

Caused by voltage-gated ion channels

Propagated along axons

Gated Channels

Chemically gated or ligand-gated channels

Ligands are chemical signals 

• Hormones or neurotransmitters

Induce opening and cause changes in cell membrane permeability

Phases of an Action Potential

Resting Phase → Rising Phase → Top of the Curve → Falling and Undershoot Phase

Resting Phase

Equilibrium between diffusion of K+ out of the cell and voltage pulling K+ into the cell

Rising Phase

Stimulus causes the threshold to be reached

Na+ channel activation gate opens

Top of the Curve

Maximum voltage reached

K+ gate opens

Na+ channel inactivation gate closes

Falling and Undershoot

Undershoot occurs as K+ diffuses out before K+ channel closes

K+ gate open

Na+ channel inactivation gate closed

Equilibrium Restored

Na+ channel activation gate closes; inactivation gate opens

Increase Velocity of Conduction

Axon has a large diameter

• Less resistance to current flow

• Primarily in invertebrates

Axon is myelinated → unique to vertebrates

• Action potential is only produced at the Nodes of Ranvier

• Impulse jumps from node to node —> Saltatory conduction

Mechanisms of Cell Communication

Direct, Synaptic, Endocrine, and Paracrine

Direct Contact Signaling

Immediate communication between adjacent cells

Key for tissue formation

Synaptic Signaling

Axons secrete chemical messengers called neurotransmitters

Short-distance travel

Transmission is usually localized to the cell that receives the neurotransmitter

Endocrine Signaling

Endocrine glands (and some organs) secrete hormones into extracellular fluid

Carried by the bloodstream but only binds to appropriate receptors

Hormone

A regulatory chemical that is secreted into the extracellular fluid and carried by the blood

Paracrine Signaling

Signaling molecules that do not travel through the bloodstream

Coordinate local physiological responses

Allow cells of an organ to regulate one another

Characteristics of Endocrine System Components

Must be sufficiently complex to convey regulatory information to their target cells

Must be adequately stable to resist destruction before reaching their target cells

Classes of Hormones

Peptides and Proteins, Amino Acid Derivatives, Steroids

Amino Acid Derivatives

Produced by enzymatic modification of amino acids

Catecholamines (Adrenaline)

Thyroid hormones

Melatonin

Steroids

Produced by modification of cholesterol

Sex steroids (Testosterone, progesterone, etc.)

Corticosteroids (Cortisol)

Lipophilic (nonpolar) Hormones

Fat-soluble

Steroid hormones and thyroid hormones

• Testosterone (and other sex hormones) is a steroid hormone

Travel on transport proteins in the blood

Bind to intracellular receptors

Tend to act over a brief time period

Regulate gene expression

Effects last hours to days

Hydrophilic (polar) Hormones

Water-soluble

Freely soluble in the blood

Bind to extracellular receptors

Tend to have a much longer active period

Lipophilic Transport

1. Hormone passes through the plasma membrane

   1. On a transport protein

   2. The membrane is fat-based, so it can pass through 

2. Inside the target cell, the hormone binds to a receptor protein in the cytoplasm or nucleus

3. The hormone-receptor complex binds to the hormone response element on DNA, regulating gene transcription

4. Protein synthesis

5. Change in protein synthesis is the cellular response

Characteristics of Hydrophilic Hormones

Peptide, protein, glycoprotein, and catecholamine hormones

Too large or polar to cross the cell membrane

• (1) Bind to receptors on the plasma membrane

• (2) Activation of protein kinases

  • Activate or deactivate intracellular proteins (3) by phosphorylation

Largest class of membrane receptors

Modern drug target