What is the function of the micturition reflex center?
Sensory impulses from the stretch receptors signal the reflex center, parasympathetic motor impulses travel to the detrusor muscle, which contracts rhythmically in response. A sensation of urgency accompanies this action Components of the micturition reflex center Nerve centers in the brainstem and cerebral cortex
Where is the micturition center in the brain?
This reflex is integrated in the pontine micturition center, which is located in the rostral brainstem. Also, a sacral micturition center is located at S2–S4, through which the bladder can contract independently of cortical and pontine input.
What is bladder emptying and micturition reflex?
Bladder Emptying and the Micturition Reflex. The micturition or emptying phase displays a coordinated relaxation of the inner and outer urethral sphincters, under sympathetic and somatic regulation respectively, with strong contractions of the detrusor muscle due to parasympathetic impulses.
What is the volume of urine that initiates the micturition reflex?
Stimulus: Volume of urine that initiates micturition reflex is 300-400 ml 2. Receptor: Stretch receptors in bladder wall 3. Afferent: Pelvic parasympathetic
Where is the micturition reflex center quizlet?
The micturition center is located in the pons of the brainstem.
What brain part controls micturition?
The neuroscience of urination. The medial prefrontal cortex (mPFC) is located behind the forehead at the front of the cortex (green), while the pontine micturition center (PMC) and the locus coeruleus (LC) are located within a part of the brainstem known as the pons (blue).
What nerve controls micturition reflex?
The micturition reflex is peripherally mediated by components of the somatic and the autonomic nervous systems. The bladder receives its motor innervation through the parasympathetic pelvic nerves.
What is the pontine micturition center?
Pontine Micturition Center. The pontine micturition center (PMC) in the brainstem is activated via afferent signals from the urinary bladder as it is filling. This center sends inhibitory impulses to the spinal reflex arcs to enable bladder voiding. In the absence of any other regulation, the afferents from the bladder and urethra to ...
What is the guarding reflex?
Urethral reflexes, called ‘the guarding reflex,’ also play a part in inhibiting involuntary bladder emptying during this process. The afferents are all conveyed through the pelvic nerves to initiate a spinal reflex.
What is the detrusor in the bladder?
The detrusor is the smooth or involuntary muscle of the bladder wall. The urethral muscles consist of the external and internal sphincter. The internal sphincter and detrusor muscle are both under autonomic control. The external sphincter, however, is a voluntary muscle under the control of voluntary nerves.
What is the term for the relaxation of the striated sphincter?
Micturition is thus characterized by: relaxation of the striated sphincter (somatic innervation) relaxation of the smooth muscle sphincter and opening of the bladder neck (sympathetic innervation) detrusor contraction (parasympathetic innervation) The distension of the urinary bladder wall causes wall tension to rise very slightly.
What is the act of micturition?
The act of micturition is an autonomic reflex at the level of the spinal cord. This reflex also helps to complete micturition when the act is voluntarily initiated, or when it follows a period of inhibition by the brain, by relaxing the external sphincter. The control of this process is mediated via afferent signals from stretch ...
Where do impulses from the bladder go?
Impulses from the filling bladder are carried to the spinal cord via the pelvic and hypogastric nerves, whereas the pudendal and hypogastric nerves carry impulses from the neck of the bladder and the urethra.
Does cortical control override micturition?
Afferent firing frequency increases with filling, but cortical control still overrides the micturition reflex until voluntary voiding is determined upon. During micturition, urinary flow is assisted by additional detrusor contractions and external sphincter relaxation which further lowers resistance to the passage of urine.
Which nerves inhibit the micturition reflex?
This control is aided by nerve centers in the brain stem and cerebral cortex that can partially inhibit the micturition reflex throught the pudendal nerve. Nerve centers within the pons and hypothalamus function to make the micturition reflex more effective.
How do cortical areas prevent micturition?
They partially inhibit the reflex except when micturition is desired. They can prevent micturition by contraction of external urethral sphincter. When it is time to urinate, the cortical areas facilitate the sacral centre to initiate micturition reflex and inhibit the external urethral sphincter.
Introduction
Micturition, also known as urination, is the process of expelling urine from the bladder. The purpose of urination is to eliminate metabolic products and toxic wastes from the body that have been filtered from the blood by the kidneys.
Relevant Anatomy & Physiology
The urinary tract comprises of two mutually dependent components: the upper tract, which contains the kidneys and ureters, and the lower tract consisting of the bladder and urethra. The lower tract is involved in the micturition reflex.
Mechanism
Micturition is a complex and highly distributed process, involving pathways at multiple levels of the brain, spinal cord and PNS, in addition to being mediated by multiple neurotransmitters. At the most basic level, the micturition reflex is triggered when the bladder fills with urine.
What is the name of the cell that controls the micturition of the brain?
Pontine micturition center. The Pontine micturition center (PMC, also known as Barrington's nucleus) is a collection of neuronal cell bodies located in the rostral pons in the brainstem involved in the supraspinal regulation of micturition. When activated, the PMC relaxes the urethral sphincter allowing for micturition to occur.
Which neurons control the detrusor muscle of the bladder?
In humans and other mammals, neurons in the PMC send descending excitatory projections to spinally located parasympathetic neurons controlling the detrusor muscle of the bladder and inhibitory interneurons regulating Onuf's nucleus.
What is the function of the PMC?
The PMC coordinates with other brain centers , including the medial frontal cortex, insular cortex, hypothalamus and periaqueductal gray (PAG). The PAG acts as a relay station for ascending bladder information from the spinal cord and incoming signals from higher brain areas .
