Human Bio Ex 3

What is one characteristic all forms of cancer share?

uncontrolled cell division

Tumor (neoplasm)

an abnormal growth of cells

two basic types of tumors

1. benign

2. malignant

Benign tumor

• abnormal mass of tissue surrounded by a capsule of connected tissue

• usually remains at the site where it forms

• often can be removed completely by surgery

malignant tumor

• invades surrounding tissue

• speads to multiple locations (=metastasis)

• cancerous

Stages of cancer development

1. Dysplasia in tissues of precancerous cells

2. carcinoma in situ

3. development of blood supply

4. metastasis

dysplasia

• precancerous cells look different from normal cells

• form a disorganized clump of cells

carcinoma in situ

• tiny mass only a mm or two in diameter (about the size of a BB)

• tumor attracts a blood supply

metastasis

cancer cells leave original tumor and enter either the cardiovascular or lymphatic systems and travel to distant sites

circulatory

______ patterns often explain patterns of metastasis

programmed cell division

in normal cells ______ is initated when genes regulating cell division have been damaged

self-destruct

cancer cells do not _____ when their DNA is damaged

Known causes of cancer

Genetic changes that turn normal cells into cancer cells are usually brought about by:

• viruses: i.e. HPV

• mutations: caused by exposure to certain chemicals or radiation

Treating cancer

1. surgery

2. radiation therapy

3. chemical therapy

Surgery

• performed when tumor is accessible & can be removed without damaging vital tissue

• complete cure possible with early tumors (no spread)

Radiation

• used when cancer has spread from initial site but is still localized

• typically follows surgery

• radiation damages DNA and extensive damage triggers apoptosis

chemotherapy

• used when cancer has spread at diagnosis

• used to kill rapidly dividing cells throughout the body

• actions of drugs

  • block DNA synthesis

  • damage DNA

  • prevent cell division

function of the nervous system

integrate and coordinate the body with the brain and spinal cord

divisions of the nervous system

• CNS- central nervous system: brain and spinal cord

• PNS- peripheral nervous system: all of the nervous tissue outside of CNS

Composition

• neurons

• neuroglial cells

neurons

excitable cells that send messages

neuroglial cells

• outnumber neurons by 10:1

• several types, each with a specific function

• provide structural support, growth factors, insulating sheaths around axons

three categories of neurons

1. sensory

2. motor

3. interneurons

sensory neurons

carry information toward the CNS from sensory receptors

motor neurons

carry information away from the CNS to an effectori

interneurons

• only found in CNS

• b/t sensory and motor neurons

• integrate & interpret sensory signals from sensory receptors

• account for more than 99% of the body’s neurons

dendrites

• receive signals from other cell like neurons or from the environment

• carry information toward the cell body of a neuron

axon

carries information away from cell body to either another neuron or effector

cell body

• contains nucleus & other organelles

• functions to maintain the neuron

nerves

• consists of parallel axons, dendrites, or both from many neurons

• covered w/ a tough connective tissue

• classified as sensory, motor, or both

the role of the myelin sheath

provide electrical insulation that increases the rate of conduction in a nerve impulse

nodes of Ranvier

gaps b/t adjacent Schwann cells

saltatory conduction

jumping from one node of Ranvier to the next, resulting in messages traveling faster

multiple sclerosis

• a disease in which the myelin sheath in the brain & spinal cord are progressively destroyed

• results from the destruction of the myelin sheath that surrounds the axons in the CNS

scleroses

the scars on the MS that interfere w/ the transmission of nerve impulses

action potential (nerve impulse)

an electrochemical signal caused by Na⁺ and K⁺ crossing the neurons membrane to enter & leave the cell

synaptic transmission

communication b/t a neuron and an adjacent cell occurs by neurotransmitters

synapse

junction b/t a neuron and another cell

synaptic cleft

• gap b/t 2 cells

• neurotransmitters diffuse across the gap

• in the case of 2 neurons: the presynaptic neuron sends a message to the postsynaptic neuron

synaptic knob

swelling at the end of the axon of the presynaptic neuron

at an excitatory synapse

binding of the neurotransmitter to the receptor causes sodium channels to open, increasing the likelihood that an action potential will begin

at an inhibatory synapse

• binding of the neurotransmitter ot the receptor opens different ion channels

• the postsynaptic cell’s interior becomes more negatively charged than usual, reducing the likelihood that an action potential will begin

summation

• combined effects of excitatory & inhibitory effects at any given moment at the same time

• determines whether an action potential is generated

• this level of integration provides fine control over neuronal responses

removal of neurotransmitters

• temporary effects

• once neurotransmitters released into a synpase, they are quickly removed

• some are deactivated by enzymes

• others are pumped back into the synaptic knob of the presynaptic axon

roles of neurotransmitters

some neurotransmitters produce different effects on different types of cells

acetylcholine

• acts in both the PNS and CNS

• released at every neuromuscular junction

myasthenia gravis

autoimmune disease that attacks the acetylcholine receptors at neuromuscular junctions, resulting in little muscle strength

norepinephrine

regulates mood, hunger, thirst & sex drive

serotonin

promotes a feeling of well-being

dopamine

regulates emotions & complex movements

alzheimers disease

associated w/ decreased levels of acetylcholine

clinical depression

associated with decreased levels of serotonin, dopamine, & norepinephrine

parkinson’s disease

associated with decreased levels of dopamine