Human Bio Exam 3

Motor neurons

PNS neurons that receive CNS output information and carry signals to muscle cells instead of neurons

Involuntary reflexes

Control of skeletal muscle contractions that bypass the brain

Key functions of muscles

Movement, posture, blood circulation, keeping bones in place

How do muscles move?

They contract/shorten

Tendon

Tissue attaching bone and muscle

Muscle

Muscle fiber

Muscle cell (has more than one nucleus)

Myofibril

The long rod-like tissue inside of muscle cells; contains sarcomeres

Sarcoplasmic reticulum

ER for muscles (stores calcium ions)

Actin

Filament for muscle contraction

Myosin

Motor protein for contraction; uses ATP

Sarcomere

Functional unit of striated muscle; contains actin and myosin

Neuromuscular junction

The space that mediates stimulation

Slow-twitch (type I) fibers

Small diameter fiber cells that can contract incrementally for a relatively long time

Fast-twitch (type II) fibers

Large diameter fibers that contract in short bursts

Hypertrophy

The more stress placed on muscle fibers, the more they will adapt by increasing their myofibril content

Atrophy

Wasting away of muscles, breakdown of myofibril content, and lack of myofibril production

Nerve

Contains axons of many neurons wrapped together in a protective sheath; carries information to and from the CNS

Reflex arc

In response to pain receptors in the sensory PNS, the spinal cord directs motor neuron in the motor PNS to avert the painful stimulus

Brain

Receives information from many sources simultaneously then integrates information and responds

Cerebellum

Receives sensory neuron information to determine spatial awareness and body positioning

Introception

Hunger, thirst

Proprioception

Sense of the body positioned in space

Medulla oblongata

Connects directly to spinal cord and controls many of the automatic functions of the body

Midbrain

Relays signals from the body to their appropriate destinations in the forebrain

Thalamus

Receives and relays sensory information but can also filter incoming sensory signals

Frontal lobes

Interpreting emotions, building memory, and future planning

Sensory neuron

Specialized cell that detects a stimulus and turns it into an action potential

Retina

Light sensitive sheet of neuronal tissue lining of the eye

Optic nerve

Sends visual signals to the brain

Farsighted

Trouble seeing near

Nearsighted

Trouble seeing far away

Astigmatism

Trouble with depth perception

Cone cells

Detect different colors and require brightly lit environments

Rod cells

Detect dim light and are used for low light

Color blindness

A mutation in the gene that influences cone cells and limits ability to sense light waves within a range of wavelengths

Auditory canal

Directs sound waves to the tympanic membrane

Tympanic membrane

Separates outer ear from middle ear, vibrates in response to sound waves

Odorant receptors

Transmembrane proteins that are highly specific to chemical and generate an action potential

Taste bud

Barrel shaped structures that consist of many chemoreceptor cells

5 taste qualities

Sour, salty, sweet, bitter, umami

Endocrine system

Makes hormones that are used for communication between cells in distant parts of the body via the bloodstream

Hormones

Chemical messengers made by endocrine glands; acts on specific cells that have a receptor for that particular hormone; circulate in the bloodstream

Endocrine glands

Organs that produce and then secrete hormones directly into the blood

Exocrine glands

Produce and then secrete substances via ducts

Role of endocrine system

Development and homeostasis

Negative feedback

Able to detect deviation from normal and counteract it; maintains homeostasis

4 components of negative feedback

Controlled variable, sensor, control center, effector

Hypothalamus

Maintains homeostasis by sensing changes and issuing commands

Pituitary gland

“Master gland”; responds to signals from the hypothalamus

Posterior pituitary

Stores hormones

Anterior pituitary

Makes hormones

Releasing hormones

Stimulate the release of other hormones

Inhibiting hormones

Reduce the production of other hormones

Neuroendocrine cells

Neurons that release hormones instead of neurotransmitters

Thyroid gland

Produces thyroxine which increases metabolic rate by causing body cells to make ATP from glucose

HPA axis

Fight or flight system; involves nervous system and endocrine system

Stages of human life cycle

Infancy, childhood, adolescence, adulthood

Adolescence

Second period of rapid growth in humans

Puberty

The physical ability to reproduce; onset during adolescence

Primary sexual characteristics

Increased growth of the genitals, ability to produce gametes

Secondary sexual characteristics

Traits that differentiate the sexes but not directly involved in reproduction

Germline mutations

Mutations are inherited and pass onto the next generation; all cells carry mutation

Soma mutations

Mutations do not pass on to the next generations; affect the bodily regions associated with the mutated cell type

Function of reproduction

Goal of making and joining sperm and egg in an environment that can support development of a new individual

Asexual reproduction

Reproduction where a single parent produces genetically identical offspring without the involvement of gametes or fertilization

Costs of sex

Energetic/ecological, genetic, reproductive

Semen

Fluid that provides energy for sperm motility and nutrients for sperm health

Testes

The site of sperm production

Spermatogonium

Stem cells that divides via mitosis to become a spermatocyte

Spermatocyte

Cell that will undergo meiosis to create 4 sperm cells

Acrosome

Enzymes for fertilization

Midpiece

Energy (mitochondria)

Flagella

Swimming

Seminal vesicles

Produce watery fluid with fructose and lipids

Prostate gland

Contributes an alkaline compound to neutralize acids in female reproductive tract

Bulbourethral gland

Make fluid to aid sperm exit from body

Penis

Ensures that sperm are delivered near the female cervix for increased odds of fertilization

Female reproductive system goal

Make and release an egg via ovulation and prepare a suitable environment for fetus if egg is fertilized

Follicle

Sac in the ovaries that contains the egg

Corpus luteum

Produces progesterone that prepares the uterus for the possibility of pregnancy

Endometrium

Lining of uterus where embryo is implanted

Polyspermy

Potential to be fertilized by more than 1 sperm

The process of fertilization

The meeting of sperm and egg

Ansiogamy

Differing size of sex cells

Acrosome reaction

Head of sperm releases enzymes that break down egg’s protective layer

Cortical reaction

Triggers cascade that causes outer envelope of the egg to harden and not react with any more sperm

Homologous chromosome

One member of each pair is inherited from each parent; look alike

Genes

Stretches of DNA that code for specific proteins

Locus

The specific location of a gene on a chromosome

Alleles

Alternative versions of the same gene at the same locus between homologous chromosomes

Meiosis

Produces cells that may participate in sexual reproduction; halves the number of chromosomes

Meiosis outcomes

Reduction of chromosome content to half; independent assortment of chromosomes; crossing over that creates new combinations of genes

Independent assortment

A mechanism of generating variable sperm/egg; random sorting of chromosome version during gamete formation

Crossing over

Because genes are in the same location on every chromosome, they can swap regions during meiosis

Evolution

When the genetic composition of a population changes over time

Populations

Groups of interbreeding individuals in the same time and place

Rules of evolution

Individuals do not evolve, populations evolve; evolving populations change genetically from one generation to the next; any genetic changes have to be inherited across generations

Evolutionary forces

Things that change genetic composition; can create/introduce new alleles or get rid of them

Mutation

Generates diversity by adding new alleles to population if transmitted through the germline; accumulate over time