Thermoregulation, tissues, and some neurons

Ectotherm

Obtains heat from environment

Endotherm

Generates heat metabolically

Torpor

Period of inactivity w/different temperatures: hibernation and estivation

Ways of changing heat conductance

Fur & feather fluffing, blubber, minimizing heat uptake, and redirecting blood flow

Fur & feather fluffing

Increase insulation volume. Traps stable layer of still air and escaping heat gets trapped in it.

Blubber

Layer of fat as insulator. Blood can be flowed beneath the fat to insulate

Minimizing heat uptake

Using a highly reflective surface on back to prevent warming from direct sun radiation

Blood flow redirection

Using vasodilation and vasoconstriction to move flow superficially or deeper

Vasoconstriction

Vessel constricts, flow in those vessels is reduced and moves elsewhere.

When body temperature is high

Larger superficial vessel diameter. More peripheral flow and more heat loss through skin

When body temperature is low

Larger internal vessel diameter. Core flow shunting and more heat conserved

Countercurrent heat exchange

Outward warm flow to extremities and cold blood returns back and is reheated in the core before going back out

Concurrent heat exchange

Both flows going in the same direction. Temperature gradient. Quickly falls

Thermoregulation

Based on negative feedback loop. Thermoreceptors detect shifts and signals integrated by the hypothalamus

Methods of thermoregulation

Vascular changes, evaporative cooling, metabolic heat, and behavior

Four basic tissues

Epithelial, connective, muscle, and nervous

Epithelial

Forms protective, secretory, and absorptive covering. Three types: squamous, cuboidal, columnar

Squamous

Flattened cells. Line blood vessel walls and air sacs in lungs

Cuboidal

Cubelike cells. Can have microvilli. Secretion and absorption

Columnar

Tall, slender cells. Can have microvilli and line the gut and respiratory tracts. Secretion and absorption

Endothelium

Thin inner lining of blood vessel. Interface between blood and vessel wall. Vascular tone, permeability, and immune response

Connective tissue

For support and structural integrity. Loose, fibrous, cartilage, and bone tissue

Loose connective tissue

Fibroblasts surrounded by collagen and elastin. Under the skin and epithelia. For support, elasticity, and diffusion

Fibrous connective tissue

Long rows of fibroblasts surrounded by collagen and elastin. Make tendons and ligaments for strength and elasticity

Cartilage

Chondrocytes in collagen matrix and chondroitin sulfate. Ends of bones, nose, ear, and more. For support, flexibility, and joint movements

Bone tissue

Osteocytes in collagen. Bones. For movement, support, and protection

Tendons

Attach muscle to bone

Ligament

Attach bone to bone

Adipose tissue

Stores energy in fat deposits. Thermal insulation and cushion

Blood

Nutrients, gas, and waste transportation. In a plasma matrix

Muscle tissue

Contractile tissue for movement and force generation. Locomotion. Skeletal muscles, cardiac muscles, and smooth muscles

Nervous tissue

Signal transmission

Organs

Combination of multiple tissue types for form specialized structures

Types of neurons

Afferent, interneurons, and efferent neurons. Motor neurons

Glial cells

Non neuronal cells. Provide nutrients and support. Ependymal, microglia, astrocyte, satellite, Schwann, oligodendrocyte

Ependymal

Makes CSF

Microglia

Phagocytic cells. Ingest and breakdown pathogens and waste in CNS

Astrocyte

In CNS. Cover blood vessels. Structural support and maintain ion concentration in intestinal fluid

Satellite

Similar functions to astrocytes, but in PNS

Schwann

Make PNS myelin sheaths

Oligodendrocytes

Make CNS myelin sheaths

Node of Ranvier

Gaps in myelin that expose axonal membrane

Presynaptic cell

Transmitting

Postsynaptic cell

Receiving

Axon hillock

Convergence point of all signals from dendrites and soma

Types of connections

Axodendritic, Axosomatic, and Axoaxonic

Electrical synapses

Direct contact and use gap junctions to pass electrical impulses. Cardiac and some smooth muscles. Fast but non modulatory

Chemical synapses

Small gap. Impulse from axon causes release of neurotransmitters which bind to postsynaptic cell and cause changes. Slower than electrical, but can be modulated.

Membrane potential

Difference in electrical charge between both sides of the membrane. Movement of ions across membrane governed by concentration and electrical field (Electrochemical gradient).

Resting potential

-70mV. Due to uneven distribution of sodium and potassium ions from the Na+/K+ pumps, the membrane being more permeable to K+ and more K+ outside than Na+ in meaning outside is more positive and inside is more negative. No net flow of ions across membrane

Equilibrium potential

Voltage gradient of ion balances its concentration gradient. No net flow of ions

Nernst equation

For prediction equilibrium potential of a cation. E(K+) = -90mV. (presence of some Na+ ions means membrane potential increases to -70mV at resting).

Goldman equation

Predicting membrane potential when the membrane is permeable to multiple ions