Source

File: wp-includes/ms-blogs.php

function update_blog_option( $id, $option, $value, $deprecated = null ) {
	$id = (int) $id;

	if ( null !== $deprecated ) {
		_deprecated_argument( __FUNCTION__, '3.1.0' );
	}

	if ( get_current_blog_id() == $id ) {
		return update_option( $option, $value );
	}

	switch_to_blog( $id );
	$return = update_option( $option, $value );
	restore_current_blog();

	return $return;
}