Untitled Quiz

Nerve Tissue

• Nerve cells are neurons, or nerve fibers
• Neurons are made of a cell body containing the nucleus, dendrites, and axons
• Neurons are found in the central nervous system or near it in the body's trunk

Nerve Tissue

• Dendrites transmit impulses to the cell body
• An axon transmits impulses away from the cell body

Types of Neurons

• Sensory neurons (afferent) carry impulses from receptors to the CNS
• Motor neurons (efferent) carry impulses from the CNS to effectors
• Interneurons are nerve cells entirely within the CNS; some are involved in thinking, learning, and memory

Nerve Tissue

• Axons and dendrites are wrapped in Schwann cells
• These layers form the myelin sheath, electrically insulating neurons

Synapses

• Neurotransmitters diffuse across synapses and bind to receptor sites on the postsynaptic neuron
• This process continues along the neurons' axons to the next synapse
• Chemical inactivators quickly deactivate neurotransmitters, preventing unwanted impulses

Synapses

• Neurotransmitters ensure one-way transmission of impulses
• Acetylcholine is a neurotransmitter in the CNS and much of the PNS
• Cholinesterase is the inactivator of acetylcholine

Spinal Cord

• The spinal cord transmits impulses to and from the brain, and is the integrating center for spinal reflexes
• It is enclosed in the vertebral canal and meninges, well-protected from mechanical damage
• It extends from the foramen magnum of the occipital bone to the disc between the first and second lumbar vertebrae

Spinal Cord

• Ascending tracts carry sensory impulses to the brain
• Descending tracts carry motor impulses away from the brain
• The central canal contains cerebrospinal fluid and is continuous with the brain's ventricles

Spinal Cord Reflexes

• Spinal cord reflexes are involuntary responses to stimuli
• They don't depend directly on the brain, but the brain can inhibit or enhance them

Reflex Arc

• A reflex arc has five essential parts:
• Receptors detect a change and generate impulses
• Sensory neurons transmit impulses from receptors to the CNS
• The CNS contains one or more synapses
• Motor neurons transmit impulses from the CNS to the effector
• The effector performs its characteristic action

The Brain

• The medulla oblongata extends from the spinal cord to the pons, anterior to the cerebellum
• It contains cardiac centers, vasomotor centers, and respiratory centers, as well as centers for cough, sneezing, swallowing, and vomiting

The Brain

• The pons bulges anteriorly from the upper part of the medulla
• It contains two respiratory centers that work with those in the medulla to produce a normal breathing rhythm

The Brain

• The thalamus is superior to the hypothalamus and inferior to the cerebrum
• It processes sensory information and transmits it to the cerebrum for interpretation

The Brain

• The cerebellum is separated from the medulla and pons by the fourth ventricle
• It's inferior to the occipital lobes of the cerebrum
• It controls movement, coordination, muscle tone, and the appropriate movement trajectory and endpoint, as well as posture and equilibrium
• It operates involuntarily, below the level of conscious awareness

The Brain

• The hypothalamus is superior to the pituitary gland and inferior to the thalamus
• It produces the antidiuretic hormone (ADH) and oxytocin
• It produces releasing hormones that stimulate the secretion of hormones by the anterior pituitary gland

Hypothalamus Functions

• Regulates body temperature by promoting responses such as sweating or shivering
• Regulates food intake
• Integrates the autonomic nervous system, and regulates organs like the heart, blood vessels, and intestines

Hypothalamus Functions

• Stimulates visceral responses during emotional situations
• Regulates bodily rhythms, including hormone secretion, sleep cycles, and changes in mood and alertness

The Brain

• The cerebrum is the largest part of the brain, with two hemispheres separated by the longitudinal fissure
• The corpus callosum, a band of 200 million neurons, connects the right and left hemispheres
• Each hemisphere has a lateral ventricle

Frontal Lobes

• Motor areas generate impulses for voluntary movement
• The frontal lobes are primarily responsible for precise movements, particularly of the hands and face
• The left motor area controls the right side of the body, and the right motor area controls the left side

Frontal Lobes

• Premotor areas are anterior to the motor areas
• They are concerned with learned motor skills, like shoe-tying
• Broca's motor speech area controls the movements needed for speaking

Parietal Lobes

• General sensory areas receive impulses from receptors in the skin
• These areas interpret cutaneous sensations
• Parietal areas receive impulses from stretch receptors in muscles
• They process body sensations
• They overlap with temporal areas to receive taste from taste buds

Temporal Lobes

• Olfactory areas receive impulses from receptors in the nasal cavities
• These areas process smells
• Auditory areas process sounds coming from inner ears
• Speech areas are involved in thought before speech

Occipital Lobes

• Impulses from the eye retinas travel along the optic nerves to visual areas in the occipital lobes
• These areas process spatial relationships, judging distance, and form three-dimensional perceptions

Association Areas

• Association areas are involved in personality, sense of humor, reasoning, and logic
• They are also responsible for learning and memory
• The hippocampus is involved with memory processing

Basal Ganglia

• Paired masses of gray matter in the cerebral hemispheres
• They are involved with the subconscious aspects of voluntary movement and work with the cerebellum
• They regulate muscle tone and coordinate auxiliary movements like arm swinging

Corpus Callosum

• The corpus callosum is a band of nerve fibers that connects the left and right cerebral hemispheres
• It enables communication between the hemispheres

Meninges and Cerebrospinal Fluid

• Meninges are connective tissue coverings of the brain and spinal cord
• Dura mater is the thick outermost layer that lines the skull and vertebral canal
• Arachnoid mater is the middle layer, made of web-like strands of connective tissue
• Pia mater is the innermost, thin membrane covering the spinal cord and brain
• The subarachnoid space between the arachnoid and pia mater contains cerebrospinal fluid

Choroid Plexus

• Choroid plexus is a network of capillaries that forms cerebrospinal fluid (CSF) from blood plasma
• CSF circulates within and around the central nervous system (CNS)
• Some CSF is reabsorbed by the arachnoid villi into the blood in cranial venous sinuses

Blood Types

• ABO blood groups: Type A blood has A antigens on its cells.
• Each person has antibodies for all blood types they don't possess
• Incorrect blood transfusions can cause blood cell clumping and rupture, leading to kidney damage and renal failure
• Blood types are A, B, AB, and O
• O is the universal donor
• AB is the universal recipient

RH Factor

• Rh positive blood cells have Rh antigens
• Rh negative recipients receiving Rh positive blood can develop antibodies, causing problems in subsequent transfusions
• This can lead to a transfusion reaction with hemolysis (red blood cell destruction) and kidney damage

Mediastinum and Pericardial Membranes

• The mediastinum is a region in the chest
• There are several pericardial membranes including fibrous, parietal, and visceral pericardium
• The membranes are filled with serious fluid

Chambers-Vessels and Valves

• The heart has four chambers made of cardiac muscle (myocardium)
• The heart's interior is lined with endocardium, which prevents clotting
• The upper chambers are atria, separated by the interatrial septum
• The lower chambers are ventricles, separated by the interventricular septum

Atrial Natriuretic Hormone (ANH)

• The atria produce ANH
• ANH release occurs when atrial walls stretch due to increased blood volume or pressure
• ANH decreases sodium ion reabsorption, which, in turn, lowers blood volume and blood pressure

Left Ventricle

• The left ventricle has thicker walls compared to the right
• This thicker wall produces more forceful contractions
• Blood from the left ventricle flows through the aortic semilunar valve to the aorta and out to the body

Heart Valves

• Information on heart valves is missing

Coronary Vessels

• Coronary vessels branch from the ascending aorta
• They branch into smaller arteries, arterioles, and capillaries supplying blood to the myocardium
• Coronary veins collect blood and empty it into the coronary sinus, leading to the right atrium

Coronary Vessels

• Blockages in coronary vessels lead to ischemia (reduced oxygen supply)
• If blood flow isn't restored, it will lead to an infarct (dead tissue)

Cardiac Cycle

• The cardiac cycle is the sequence of events in one heartbeat
• Atria contract simultaneously, followed by simultaneous ventricular contraction
• Systole is contraction, and diastole is relaxation

Cardiac Conduction

• The heart's mechanical events are regulated by electrical activity in the myocardium
• Heart cells contract spontaneously
• The heart's rhythm originates from the sinoatrial node
• The atrioventricular node, bundle of His, bundle branches, and Purkinje fibers also play a role

Arrhythmias

• Arrhythmias are irregular heartbeats, ranging from harmless to life-threatening
• Palpitations are irregular heartbeats that occur intermittently
• Fibrillation is a rapid, uncoordinated ventricular beat, ineffective at pumping blood

Heart Rate

• The average resting heart rate is 60-80 beats per minute (SA node rate)
• Bradycardia is a heart rate below 60 bpm
• Tachycardia is a heart rate above 100 bpm
• Well-conditioned individuals typically have slower heart rates

Cardiac Output

• Cardiac output is the amount of blood pumped by a ventricle in one minute
• It's calculated as stroke volume multiplied by pulse rate
• Stroke volume is the amount of blood pumped per beat
• Starling's Law of the Heart, venous return, and ejection fraction are also factors

Arteries

• Arteries carry blood from the heart to capillaries
• Smaller arteries are arterioles
• The outer and middle layers of arteries are thick

Arteries

• Arteries consist of three layers (tunica intima, tunica media, and tunica externa)

Veins

• Veins carry blood from capillaries to the heart, and smaller veins are venules
• The interior layer of veins has valves to prevent backflow
• The middle and outer layers of veins are thin due to lower blood pressure

Anastomoses

• Anastomoses are connections or junctions between blood vessels, often crucial for alternate blood flow pathways if a vessel is obstructed
• This is observed in arterial and venous systems

Capillaries

• Capillaries carry blood from arterioles to venules
• Their walls are only one cell thick, facilitating efficient material exchange with tissues
• Precapillary sphincters regulate blood flow through capillaries based on tissue needs
• Sinusoids are larger capillaries in hemopoietic tissues (bone marrow, spleen, liver, pituitary gland), allowing larger substances passage

Capillaries

• Capillaries exchange materials between blood and tissue fluids
• Diffusion moves gases from areas of high concentration to low concentration
• Blood pressure in arterioles (30-35 mmHg) is higher than tissue fluid pressure (2mmHg)

Capillaries

• Capillary blood pressure forces nutrients, plasma, and dissolved substances out of capillaries into the surrounding tissues
• Blood pressure declines as blood reaches the venous end of the capillaries
• Albumin contributes to colloid osmotic pressure, pulling fluid back into the capillaries

Capillaries

• The return of tissue fluid to the blood helps maintain blood volume and pressure
• Excess fluid enters lymph capillaries which then return to the blood as plasma

Hepatic Portal Circulation

• Blood from abdominal organs (stomach, small intestine, colon, pancreas, and spleen) is diverted through the liver before returning to the heart
• This blood flows into the superior mesenteric and splenic veins, forming the hepatic portal vein
• The portal vein delivers blood into the sinusoids of the liver to be modified before entering the heart

Hepatic Portal Circulation

• Blood in portal veins is directed into liver sinusoids for modification
• Blood then flows into the hepatic veins and returns to the inferior vena cava and right atrium
• The liver modifies blood from digestive organs and spleen

Hepatic Portal Circulation

• The liver stores or changes some nutrients
• Bilirubin from the spleen is excreted into bile and toxins are detoxified
• Alcohol is broken down in the liver and high glucose levels are converted to glycogen

Pulmonary Circulation

• The right ventricle pumps blood into the pulmonary artery
• The pulmonary artery branches into right and left pulmonary arteries, one for each lung
• In the lungs, the arteries branch into smaller arterioles and then capillaries surrounding alveoli

Pulmonary Circulation

• Alveolar exchange of gases occurs in the pulmonary capillaries.
• Oxygenated blood is collected into venules, then veins, and finally back to the heart (left atrium) via two pulmonary veins from each lung
• This oxygenated blood then enters systematic circulation

Systemic Circulation

• The left ventricle pumps blood into the aorta
• The aorta branches into the ascending aorta, aortic arch, thoracic aorta, and abdominal aorta
• The aorta's branches distribute blood to all the body through arterioles and capillaries.

Systemic Circulation

• Systemic circulation carries blood from the lower body to the inferior vena cava via blood vessels
• Systemic circulation carries blood from the upper body to the superior vena cava via blood vessels
• These return blood to the right atrium of the heart

Systemic Circulation

• Maintenance of blood pressure involves venous return (skeletal muscle pump, vein constriction, respiratory pump), heart rate and force, peripheral resistance, large artery elasticity, blood viscosity, blood loss, and hormones

Intrinsic Mechanisms of BP Regulation

• Regulating blood pressure involves the heart - Starling's law
• Kidneys' role includes blood flow and the renin-angiotensin system

Respiratory Pathways

• Respiratory pathways are a topic requiring further detail.

Pharynx

• The soft palate prevents food from entering the nasal cavity by rising when swallowing

Pharynx

• Eustachian tubes open into the nasopharynx, connecting middle ears and nasopharynx to permit air to enter/leave the middle ears and allow the eardrums to vibrate properly
• Nasopharynx is solely an air passageway

Pharynx

• Oropharynx is the passage for food and air, situated behind the mouth
• Laryngopharynx is both a food and air passage, leading to the larynx and esophagus

Larynx

• Known as the voice box, involved in speech and air passage between the pharynx and trachea
• Constructed from nine cartilage pieces connected by ligaments to prevent collapse and maintain open airways
• Thyroid cartilage is the largest, and the epiglottis sits atop the larynx

Larynx

• Vocal cords are on either side of the glottis

Trachea and Bronchial Tree

• The trachea is 4-5 inches long, connected to the larynx and primary bronchi
• Supported by 16-20 C-shaped cartilage pieces; the posterior gaps allow esophageal expansion upon swallowing
• The trachea's inner lining (mucosa) is ciliated epithelium with goblet cells to sweep mucus toward the pharynx

Trachea and Bronchial Tree

• The trachea branches into the right and left primary bronchi, which enter the lungs
• Each primary bronchus further branches into secondary bronchi that lead to the lung lobes (3 right, 2 left)
• The bronchial tree is a description of the continuous branching pattern
• The smallest branches are bronchioles that terminate in clusters of alveoli

Serous Membranes of the Thoracic Cavity

• Serous membranes (pleura) line the thoracic cavity
• Parietal pleura lines the chest wall
• Visceral pleura covers the lung surfaces
• Serous fluid between pleura prevents friction during breathing

Alveoli

• Alveoli are the functional units of the lungs
• They consist of simple squamous epithelium
• Elastic connective tissue surrounds clusters of alveoli, facilitating exhalation
• Macrophages reside in the spaces between alveoli.

Alveoli

• A capillary network surrounds each alveolus, enabling efficient gas diffusion.

Alveoli

• Each alveolus is lined with a thin layer of fluid, which includes pulmonary surfactant

Mechanism of Breathing

• Ventilation describes air movement in and out of the alveoli
• Breathing is a nervous system-controlled process using respiratory muscles
• Breathing centers in the medulla and pons generate impulses to the respiratory muscles.
• The stimulus for breathing is high CO2 levels.

Respiratory Muscles

• Diaphragm, external intercostal, and internal intercostal muscles are the primary organs of breathing

Inhalation

• Diaphragm contracts, moves downward, and expands the chest cavity
• External intercostals pull ribs up and out, further expanding the chest cavity (from side to side and front to back)
• Intrapulmonic pressure falls below atmospheric pressure
• Air flows into alveoli

Exhalation

• Impulses from the medulla decrease
• Diaphragm and external intercostals relax
• Chest cavity shrinks, and elastic connective tissue in lungs recoil
• Intrapulmonic pressure rises above atmospheric pressure
• Air moves out of alveoli

Exchange of Gases

• External respiration describes the gaseous exchange between the lungs and blood
• Internal respiration describes the exchange of gases between the blood and body tissues

Transport of Gases in the Blood

• Most oxygen is transported bound to hemoglobin in red blood cells (RBCs)
• Iron in hemoglobin enables this ability

Pulmonary Volumes

• Tidal volume, minute respiratory volume, inspiratory reserve, expiratory reserve, vital capacity, and residual air are various lung volume measures.

Acid-Base Balance

• Acidosis and alkalosis are conditions related to pH levels

Digestive System Divisions

• Digestive pathways include the alimentary tube (mouth to anus) and accessory organs
• Digestion occurs in the oral cavity, stomach, and small intestine; absorption mainly happens in the small intestine.

Digestion Types

• Mechanical digestion physically breaks down food into smaller pieces
• Chemical digestion changes complex molecules into simpler, usable forms, with enzymes assisting the process.

Teeth Structures

• Teeth function in chewing to break down food and mix it with saliva
• Tooth root is embedded in the mandible and maxillae
• Pulp cavity contains blood vessels and nerves of the trigeminal nerve
• Enamel covers the crown, offering a resistant chewing surface, and dentin forms tooth roots

Salivary Glands

• Saliva, a digestive secretion produced continuously in the oral cavity, is composed mostly of water and a small amount of digestive enzymes.

Pharynx

• Oropharynx and laryngopharynx are passageways for food.
• There is no digestion in the pharynx, just mechanical food movement.

Esophagus

• The esophagus is a muscular tube carrying food from the pharynx to the stomach.
• Peristalsis is a process propelling food, even when the food is going down.
• The lower esophageal sphincter regulates food entry into the stomach, preventing stomach content backup.

Alimentary Tube Structural Layers

• Mucosa lines the alimentary tube; epithelium secretes mucus that lubricates food passage and digestive enzymes for stomach and intestines
• Lymph nodules containing lymphocytes (antibodies) and macrophages (phagocytozing bacteria) are below the epithelium layer.

Submucosa

• Submucosa includes blood vessels, lymphatic vessels, Meissner's plexus (nerve fibers regulating secretions), parasympathetic (increase secretions), and sympathetic (decrease secretions)

External Muscle Layer

• The external muscle layer of the alimentary canal contracts to break down and mix food with digestive juices
• Peristalsis, a one-way contraction, moves food towards the anus
• Enteric nervous system functions are described: sympathetic (decrease peristalsis) and parasympathetic (increase peristalsis)

Serosa

• Serosa (mesentery and peritoneum) is a continuous serous membrane lining the abdominal cavity
• Serous fluid reduces friction between organs.

Stomach

• The stomach is a reservoir for food, initiating gradual digestion
• Mechanical and chemical digestive processes also occur.

Small Intestine

• Extending from the stomach to the cecum of the large intestine, the small intestine consists of the duodenum (first 10 inches), jejunum (8 feet), and ileum (11 feet)
• Digestion is completed in the small intestine
• The mucosa includes cells with microvilli, increasing absorption of nutrients, and goblet cells that secrete mucus

Liver

• The liver produces bile, a digestive fluid
• Bile salts emulsify fats in the small intestine mechanically

Gallbladder

• The gallbladder stores bile, receiving it from the liver's hepatic duct.
• It concentrates the bile by absorbing water.

Pancreas

• Amylase digests starch to maltose
• Lipase breaks down emulsified fats into fatty acids and glycerol
• Trypsin digests polypeptides into shorter amino acid chains
• The pancreas secretes bicarbonate to neutralize the acidic gastric juices entering the duodenum

Absorption

• Most absorption happens in the small intestine, using microvilli for increased absorption.

Liver

• Liver regulates blood glucose, amino acids, stores vitamins, and removes toxins.

Large Intestine

• The large intestine (colon) is 5 feet long, extending from the ileum to the anus
• The cecum is the initial portion; the ileocecal valve prevents backflow
• The large intestine consists of the ascending, transverse, and descending colon, sigmoid colon, rectum, and anal canal.

Large Intestine

• The appendix, a small, dead-end tube with lymphatic tissue, is attached to the cecum.
• The appendix is often surgically removed if impacted.

Large Intestine

• No digestion happens in the large intestine

Normal Flora

• Normal flora (bacteria) in colon produce and absorb vitamins, particularly vitamin K
• Colon absorption of water, minerals, and vitamins enables undigestible material elimination
• Colon functions include absorption and elimination

Defecation

• Feces composition includes cellulose, indigestible material, bacteria, and water
• Spinal cord reflex, which is sometimes voluntarily controlled, causes defecation.

Other Liver Functions

• Liver acts in carbohydrate metabolism, amino acid processing, lipid metabolism, synthesis of plasma proteins, bilirubin formation, phagocytosis, storage, and detoxification.

Kidney

• Each kidney has a hilus (indentation) on its medial side
• Renal artery supplies blood, and renal vein drains blood into the inferior vena cava
• Ureter carries urine to the bladder

Renal Corpuscle

• Renal corpuscle includes a glomerulus (capillary network from afferent arterioles, draining into efferent arterioles) and Bowman's capsule
• The structure's efferent arterioles are smaller than afferent arterioles, maintaining high blood pressure in glomeruli.

Bowman's Capsule

• Bowman's capsule is the expanded end of a renal tubule
• Its inner layer is permeable due to podocytes; the outer layer is impermeable
• Bowman's capsule has a filtrate, ultimately becoming urine

Renal Tubule

• Renal tubule continues from Bowman's capsule, consisting of several parts
• These parts include the proximal convoluted tubule (renal cortex), loop of Henle (renal medulla), and distal convoluted tubule (renal cortex)

Renal Tubules

• Distal tubules from various nephrons empty into a collecting tubule, which groups into a papillary duct to the renal pelvis
• Microvilli in proximal convoluted tubules enhance material exchange

Renal Tubules

• Peritubular capillaries surrounding the renal tubules arise from efferent arterioles
• These capillaries reabsorb materials filtered from the tubules

Blood Vessels in the Kidney

• Branches from the abdominal aorta form the renal artery
• The smallest arteries lead to afferent arterioles, supplying blood to the renal cortex
• Afferent arterioles supply blood to glomeruli, efferent arterioles supply blood to peritubular capillaries, then veins, leading to the renal vein, and finally the inferior vena cava.

Capillary Function

• Two sets of capillaries exist for material exchange
• Glomerular filtration, tubular reabsorption, and tubular secretion combine to form urine from blood plasma

Formation of Urine

• Glomerular filtration, tubular reabsorption, and tubular secretion collectively perform urine formation

Glomerular Filtration

• Blood pressure filters plasma, dissolved substances, and small proteins from the glomeruli into Bowman's capsule to form renal filtrate
• Blood pressure is greater in glomerular capillaries (60mmHg)

Glomerular Filtration

• Pressure inside Bowman's capsule is low and permeable.
• 20-25% of blood becomes filtrate inside Bowman's capsules.
• Blood cells and proteins remain in the blood.
• Waste products, nutrients, and minerals are also present in the filtrate.

Glomerular Filtration Rate

• Glomerular filtration rate (GFR) is the rate of filtrate produced by kidneys in one minute, averaging 100-125 ml
• It's affected by changes in blood flow

Tubular Reabsorption

• Tubular reabsorption occurs from renal tubules into the peritubular capillaries
• The kidneys produce 150-180 liters of filtrate daily, with 1-2 liters the typical output

Tubular Reabsorption/Secretion

• Most reabsorption and secretion happens in the proximal convoluted tubules because of microvilli
• Distal and collecting tubules play a role in reabsorption as well

Mechanisms of Reabsorption

• Active transport uses ATP to move useful materials from the filtrate back into the blood
• This includes glucose, amino acids, vitamins, and positive ions
• Reabsorption thresholds exist
• Reabsorption of calcium (Ca), sodium (Na), and excretion of potassium (K) are specific examples

Mechanisms of Reabsorption

• Passive transport (osmosis, pinocytosis) is also involved

Tubular Secretion

• Active secretion of substances (like ammonia, creatinine, drugs, and hydrogen ions) into the renal filtrate happens through peritubular capillaries to adjust blood pH

Kidney Acid-Base Balance

• Kidneys regulate blood acidity bysecreting more hydrogen ions into the filtrate and returning bicarbonate to the blood (acidity) or secreting more bicarbonate into the filtrate and returning Hydrogen ions to the blood (alkalinity)

Other Kidney Functions

• Kidneys produce renin, erythropoietin, and activate Vitamin D.

Urinary Bladder

• The bladder acts as a reservoir for collected urine, which it expels when full
• Mucosa with transitional epithelium allows expansion without tearing
• The trigone, a triangular area on the bladder floor, lacks rugae and doesn't expand
• Urinary bladder openings (ureters, urethra) are located at the points of a trigone

Urinary Bladder

• The internal sphincter is formed from detrusor muscle around the urethra opening
• The external sphincter, composed of skeletal muscle, is under voluntary control

Urethra

• The urethra carries urine from the bladder to the outside of the body
• The external sphincter, composed of skeletal muscle, is under voluntary control

Urination Reflex

• Urination is also known as micturition or voiding
• It is a spinal cord reflex that can be influenced voluntarily.
• Bladder stretching initiates the reflex, activating the detrusor muscle to contract
• The reflex typically activates before the bladder reaches a full (800 ml) capacity.

Urination Reflex

• Stretching of the bladder generates sensory signals that reach the spinal cord and trigger motor impulses
• These motor signals cause detrusor muscle contraction, emptying the bladder
• Simultaneously, the external sphincter relaxes (voluntarily) allowing urine to flow into the urethra and bladder emptying to occur.