cardiac & smooth muscles

smooth muscle

found in numerous hollow organs; not controlled by conscious movement (instead the nervous system gives direction)

smooth muscle is also known as…

non-striated involuntary muscle/involuntary muscle

cardiac muscle

found only in the heart; controlled by itself & nervous system

cardiac muscle is also known as…

involuntary striated muscle

cardiac & smooth muscle both have what type of nucleus?

single

cardiac muscle makes of the bulk of…

cardiac tissue (heart)

what shape & size describes cardiac muscles?

longer than they are wide, have branches, & joined by intercalated discs.

intercalated discs

join each cardiac muscle to each other; helps signal travel from 1 muscle cells to the next; act as 1 large unit

internal metronome

keeps a set time (fastest group of cardiac muscle cells sets the pace)

cardiac muscles follow their own mini…

internal nervous system allowing independent contractions

SA (sino atrial) node

in the right atrium of the heart; fastest groups of cells become this; beginning of the mini internal nervous system

autonomic nervous system

automatic, no conscious control

sympathetic nervous system

fight, flight, freeze, or fawn

parasympathetic nervous system

rest & digest

what are the 2 types of the autonomic nervous system?

sympathetic & parasympathetic

somatic nervous system

under conscious control, given a directive & it is carried out

smooth muscle is controlled by…

the autonomic nervous system (combined brain & spinal cord)

when in fight, flight, freeze, or fawn (sympathetic nervous system)…

the GI is not focused on digesting food

visceral smooth muscle

large sheets of cells; single units; walls of hollow organs

multi-unit smooth muscle

small discrete grouping; found in the eye; responsible for small, minute movements

the more nerves per muscle means…

the finer/more precise the movements

what shape & size describes smooth muscles?

tapered at each end; actin & myosin are like a fishnet like pattern around the muscle cell

dense bodies

the connection/anchor points where the “fish net” sits on the outside of actin & myosin filaments; where actin & myosin “click together” around the cell

when smooth muscle contracts…

the “fishnet” of actin & myosin squeezes the cell

how do visceral smooth muscle contracts?

sheets move like waves to move things along/through organs

peristalsis

wave-like muscular contractions that move food, waste, & other substances through organs like the digestive & urinary tract

parturition contractions

dilate the cervix & expand/stretch the pelvic floor muscles

once the uterus is empty after parturition…

progesterone comes in & stops smooth muscle contraction

the urinary bladder has stretch receptors that cause…

signal to be sent to the brain saying that urine needs to be released (when bladder is ~75% full)

the GI tract has stretch receptors that cause…

signal to be sent to the brain saying that the stomach is empty/stomach is full & whether or not to eat/stop eating

how do multi-unit smooth muscles contract?

small, delicate grouped movements; cannot occur without the autonomic nervous system

multi-unit smooth muscle contractions in the eye…

sympathetic = dilation of the pupil

parasympathetic = contraction of pupil

when eating very quickly…

the brain does not receive signals fast enough to understand that the stomach is full

when signals are released to the visceral smooth muscles during parturition…

the GI tract & uterus all contract & move together as 1 big piece