Bio 30-Nervous and Endocrine System

Homeostasis

maintaining a constant internal environment by adjusting to changes

Central Nervous System (CNS)

consists of the brain and spinal cord

Peripheral Nervous System (PNS)

-carries information between organs and CNS

-nerves outside of the brain and spinal cord

Neurons

functional unit of the nervous system

Glial Cells

-structural support

Dendrites

branchlike parts of a neuron that are specialized to receive information and send it toward the cell body

Axon

conducts nerve impulses away from cell body toward other neurons or to effectors

Myelin Sheath

-formed by Schwann cells

-only in PNS

-glistening white coat of fatty protein that acts as insulator

-speeds up nerve impulse by causing Saltatory conduction (making it jump)

Nodes of Ranvier

-gaps in the myelin sheath

-speeds up nerve impulse by causing Saltatory conduction (making it jump)

Neurilemma

-thin outer membrane that surrounds axons

-only in PNS

-promotes regeneration

-formed by Schwann cells

-found in all PNS nerve cells

Synapse

small space between neurons or neurons and effectors

Neurotransmitters

chemicals that are released from the presynaptic neuron and then diffuse across synaptic space and causes the postsynaptic neuron to depolarize

Summation

combination of excitatory responses to trigger an 'all' response

Acetylcholine

-excitatory neurotransmitter for muscles

-can be inhibitory in some locations

Norepinephrine

involved in fight or flight response and wakefulness

Cholinesterase

-inhibitory nerotransmitter

-breaks down acetycholine to 'reset' the synapse

Spinal Cord

-carries sensory information to brain and information from the brain to motor neurons

-contains white matter (myelinated nerves) and grey matter (unmyelinated nerves)

Forebrain

the largest and most complicated region of the brain, including the thalamus, hypothalamus, and cerebrum.

Hypothalamus

-maintains Homeostasis (Autonomic)

-connects to Pituitary gland

Cerebrum

-divided into left (logical) and right (artistic) hemispheres

-largest part of the brain

-many folds to allow for more neurons

Corpus Callosum

bundle of nerves that connects left and right side of brain

Frontal Lobe

Functions:

-higher level thinking

-personality

-motor movements

Occipital Lobe

-located at the back of the head

Functions:

-vision

Temporal Lobe

Functions:

-hearing

-smell

-memory

-interpretation of sensory information

Parietal Lobe

-located at the top of the head

Functions:

-touch

-taste

-temperature

-pain

-emotions

Hindbrain

division of the brain containing the medulla, pons, and cerebellum

Pons

a brain structure that relays information from the cerebellum to the Medulla

Cerebellum

controls coordination of limb movements, balance and muscle tone

Sympathetic division

fight or flight

Parasympathetic division

rest and digest

Autonomic Nervous System

-brings information about body's internal environment to CNS

-regulates by carrying signals from CNS to muscles and organs

-composed of two divisions

Sensory-Somatic System

-bring information from external environment to CNS and send information back to muscles

-voluntary EXCEPT for reflex arcs

Sclera

-outer layer

-protection

-maintains shape

Choroid layer

-middle layer

-pigmented to prevent light from scattering

-contains blood vessels

Iris

a ring of muscle tissue that forms the coloured portion of the eye around the pupil and controls the size of the pupil opening

Lens

the transparent structure behind the pupil that changes shape to help focus images on the retina

Cornea

-the transparent outer covering of the eye

-requires oxygen and nutrients from aqueous humor

Aqueous Humor

fluid in the eye, found between the cornea and the lens that provides nutrients

Retina

-innermost layer

-contains light-sensitive photoreceptor cells called rods and cones

Rods

-black and white vision

-peripheral vision

-work well in low light intensity

Cones

-colour vision

-requires bright light

-concentrated in the Fovea Centralis

-3 types (red, green, blue)

Fovea Centralis

-small depression

-most sensitive

-packed with cones with rods surrounding perimeter

Blind Spot

-location of the optic nerve and blood vessels connecting to eye

-no room for photoreceptors on the retina

Cataracts

-lens becomes opaque and prevents light from passing through

Glaucoma

-buildup of aqueous humor in anterior chamber

-caused from blocked drainage duct and retinal cell slowly dies from pressure

-results in vision loss

Astigmatism

lens or cornea is irregularly shaped

Colourblindness

inherited condition where one lacks certain cones

Pinna

ear flaps of cartilage

Auditory Canal

-funnels sounds to ear drum

-has specialized sweat glands produce war wax

Tympanic membrane/Eardrum

the membrane at the end of the ear canal that relays vibrations into the middle ear

Ossicles

-three tiny bones in the middle ear

-specialized sweat glands produce war wax

Eustachian tube

-allows for air pressure equalization

-connected to throat

Semicircular Canal

-for balance

-3 fluid-filled rings arranged in different angles

-movement of fluid identifies body movement

Cochlea

-shaped like snail shell

-vibrations are converted into nerve impulses by organ of Corti

-comprised of rows of hair cells

Schwann Cell

-Glial cell

-non-conducting

-form the Myelin sheath

Negative Feedback

a self-regulating system in which the output is fed-back to reduce further output

Tropic Hormones

hormones that target other endocrine glands

Pituitary Gland (“The Master Gland”)

-located right below the Hypothalamus

-produces and stores hormones

Hypothalamus

-composed of an anterior and posterior lobe

-stimulate the Pituritary gland to release hormones

Pancreas

contains 2 types of cells:

1. cells that produce hormones (Insulin and Glucagon) which are located in structure called islets of Langerhans

2. cells that produce digestive enzymes

Insulin

-lowers blood sugar

-causes all cells to becomes permeable to glucose

-glucose is converted to glycogen and stored in the liver and muscles

-antagonistic to Glucagon

Glucagon

-raises blood sugar

-glycogen is broken down and releases glucose in the liver and muscles

-antagonistic to Insulin

Diabetes Mellitus

-chronic disease caused by insufficient production or use of Insulin

-3 main types

Symptoms:

-Hyperglycemia: high blood sugar

-glucose in urine and high urine production

-will feel thirsty and tired

Adrenal Medulla

-regulated by nervous system

-produces Epinephrine and Norepinephrine which both increase blood sugar and heart rate

-stimulated by Sympathetic nervous system

Adrenal Cortex

-regulated by hormones

-produces Aldosterone and Cortisol

Aldosterone

-increases blood volume and pressure

-reabsorbs sodium to increase water reabsorption

-used during long term stress

-targets Kidney tubules

Cortisol

-targets all cells

-increases blood glucose due to fats and proteins broken

Epinephrine

-targets liver, muscles and heart

-increases blood glucose due to converted glycogen

-increases heartrate

-increases blood flow to muscles

ACTH (Adrenocorticotropic hormone)

-targets Adrenal Cortex

-initiates long term stress by causing the release of Cortisol and Aldosterone

Metabolism

-chemical reactions that occur in the body to maintain life

Thyroid

-produces Thyroxin and Calcitonin

Throxine

-increases metabolism and regulates growth

-main hormone that controls metabolism

Calcitonin

-lowers blood calcium levels

-causes bones to store calcium by removing from the blood

-sourced by the Thyroid gland

Goiter

-caused by a lack of iodine in the diet

-no negative feedback so TSH continues to be released causing thyroid to enlarge

Hyperthroidism

-excessive secretion of Thyroxin

-can be caused by an autoimmune disease called Graves disease or an overactive thyroid

Symptoms:

-high body temperature

-high blood pressure

-weight loss

Hypothyroidism

-low secretion of Thyroxin

Symptoms:

-lethargy in adults

-dwarfism in infants

-low metabolism (weight gain and chills)

Parathyroid hormone (PTH)

-increases calcium in the blood

-sourced by the Parathyroid gland

Human Growth Hormone (HGH)

-released from the anterior pituitary gland

-targets most cells to stimulate growth

-breaks down fat

-increases blood glucose levels to support growth

-cells grow larger and faster

Antidiuretic Hormone (ADH)

-reduces water loss in urine when dehydrated

-produced by the Hypothalamus but stored in the posterior pituitary

-release stimulated by osmoreceptors

Blood Sugar

-glusose found in the blood

-controlled by 2 Endocrine glands (Pancreas and Adrenal glands)

Osmoreceptors

-in the Hypothalamus

-detect dehydration in the blood and cause the release of ADH and the feeling of thirst

-shrink through osmosis = stimulation

Ganglia

clusters of cell bodies outside spinal cord

Medulla Oblongata

coordinating centre for autonomic nervous system