Quest Review

1. Homeostasis

• The maintenance of a constant environment in the body

• Important for maintaining i) Temperature ii) Water levels iii) Glucose concentration iv) pH levels

Maintaining Blood pH( Respiratory system and kidneys)

• Acidosis(Low blood pH): depression of the central nervous system (creates disorientedness and comatose)

• Alkalosis(High blood pH): hyperexcitability of the nervous system

  • Creates spontaneous nervous stimulation, spasms, muscular contractions and nervousness

• Kidneys regulate blood at proximal and distal tubules

Maintaining body temperature (Integumentary System)

• Sweating: body heat stimulates sweat glands to release sweat that later evaporates

• Vasodilation: capillaries filled with blood draws closer to skin so heat is lost

• Vasoconstriction: Capillaries get constricted for blood to get taken away from the surface of the skin

• Piloerection: Hairs “stand up” to trap air that is warmed by body heat

2. Negative Feedback Systems

• Any homeostatic control system that works with three components

  • Receptor: Detects changes in the internal environment

  • Control center: processes information from the receptor

  • Effector: creates the initial response

• Small changes are prevented from being to large

3. Nervous System

• Network of specialized cells that process information and causes reactions

• Sends, receives, and processes nerve impulses to the body for organs to function

• Nerves connect the brain to the body to carry information throughout the body in the form of electrochemical signals (or impulses)

• Reflex arc: a simple nerve circuit that creates an automatic response

Neuron: structual and functional unit of the nervous system

• Afferent neurons: carries impulses from sensory receptors to the Central Nervous System

• Efferent neurons: carries impulses from the CNS to the skeletal muscles

• Interneurons: relays impulses between afferent and efferent neurons

Nerve Signaling: A membrane potential that is a localized electrical gradient

• Cations (Extracellular)

  • K⁺ the principal intracellular cation

  • Na⁺ the principal extracellular cation

• Anions (Intracellular)

  • Proteins, amino acids, sulfate, and phosphate are principal intracellular aions

  • Cl^- principal extracellular anion

Action potential: All or Nothing depolarization

• 55mV achieves a threshold potential (initial trigger)

Chemical Synapse steps

1. Action potential depolatizes the plasma membrane at the synaptic terminal

2. Action potential opens up voltage-gated Ca²⁺ channels in presynaptic terminal for an influx of Ca²⁺

3. Ca²⁺ concentration causes synaptic vesicles to fuse with the presynaptic membrane

4. Vesicles release neurostransmitters into presynaptic cleft

5. Neurotransmitters binds to receptors of ligand-gated ion channels for diffusion of Na⁺

6. Neurotransmitters release from receptors to close channels and diffuses out of the synaptic cleft or become degraded by an enzyme

Different Types of Neurotransmitters

• Acetylcholine: an excitatory neurotransmitter tjay opens up sodium ion channels for depolarization

  • Also inhibitory om cardiac muscle cells to slow down cardiac muscle concentraion, Released by botulism toxin

• Cholinesterase: released from the postsynaptic membrane to hydrolize Acetylcholine

• Epinephrine & Norepinephrine: Excitatory and inhibitory that is secreted in the CNS and PNS amd adremal glands

• Dopamine: Excitatory (sometimes inhibitory) that affects sleep, mood, attention, and learning

  • Lack of Dopamine = Parkinson’s Disease Excessive Dopamine = Schizophrenia

• Serotonin: Inhibitory, same effects as Dopamine, secreted only in the CNS

Vertebrate Nervous System

Central Nervous System (CNS)

• Brain and spinal cord

  • Contains fluid-filled spaces (cerebospinal fluid)

• White Matter: Bundles of myelinated axons

• Gray Matter: unmyelinated axons, cell bodies and dendrites

Peripheral Nervous System (PNS)

• Nerves that carry information between organs of the body and the CNS

• Somatic Nerves: controls skeletal muscles and skin

  • Sensory nerves: relays information about the environment of the CNS

  • Motor Nerves: creates a response to external stimuli

• Automatic Nerves: controls internal organs, smooth and cardiac muscle

Sympathetic Nervous System: prepares body for stress

• Dialates pupils

• Inhibits Salivary glands

• Accelerates heart

• Relaxes Bronchi

Parasympathetic Nervous System: restores normal balance

• Constricts pupil

• Stimulates salivary glands

• Slows heart

• Constricts bronchi

Left Hempishpere: controls the right side of the body

• Language, math, logic operations, motor control

Right Hempisphere: controls the left side of the body

• Pattern recognition, spatial relationships, emotions

Brain structures and roles

• Brainstem (lower brain): functions in homeostasis, coordination of movement, conduction of impulses to and from higher brain centers

• Medulla & Pons: controls automatic nerve functions, relays information to and from higher brain centers

• Cerebellum: Coordinates motor activities, relays sensory information, and coordinates motor commands

• Thalamus: relays sensory information from the cerebrum, regulates emotion and arousal

• Hypothalamus: Regulates autonomic activity, body temperature, hunger, thirst, and the pituitary gland